diff --git a/dev/js/src/match/attachement.js b/dev/js/src/match/attachement.js
index 7b6cb94..9211728 100644
--- a/dev/js/src/match/attachement.js
+++ b/dev/js/src/match/attachement.js
@@ -10,6 +10,9 @@
  * @author Nils Diewald
  */
 define(function () {
+
+  "use strict";
+
   const uriRE = new RegExp("^data: *([^;,]*?(?: *; *[^,;]+?)*) *, *(.+)$");
   const mapRE = new RegExp("^ *([^=]+?) *= *(.+?) *$");
 
@@ -24,6 +27,7 @@
 
     // Parse URI scheme
     _init : function (url) {
+      const t = this;
 
       // Decode
       url = decodeURIComponent(url);
@@ -31,39 +35,40 @@
       if (!uriRE.exec(url))
         return;
 
-      this.payload = RegExp.$2;
+      t.payload = RegExp.$2;
 
       let map = {};
       let start = 0;
-      this.base64 = false;
-      this.isLink = false;
-      this.contentType = "text/plain";
+      t.base64 = false;
+      t.isLink = false;
+      t.contentType = "text/plain";
 
       // Split parameter map
       RegExp.$1.split(/ *; */).map(function (item) {
+        const t = this;
 
         // Check first parameter
         if (!start++ && item.match(/^[-a-z0-9]+?\/.+$/)) {
-          this.contentType = item;
+          t.contentType = item;
 
           if (item === "application/x.korap-link")
-            this.isLink = true;
+            t.isLink = true;
         }
        
         // Decode b64
         else if (item.toLowerCase() == "base64") {
-          this.base64 = true;
-          this.payload = window.atob(this.payload);
+          t.base64 = true;
+          t.payload = window.atob(t.payload);
         }
 
         // Parse arbitrary metadata
         else if (mapRE.exec(item)) {
           map[RegExp.$1] = RegExp.$2;
         };
-      }.bind(this));
+      }.bind(t));
 
-      this.param = map;
-      return this;
+      t.param = map;
+      return t;
     },
 
     /**
@@ -72,8 +77,8 @@
      */ 
     inline : function () {
       if (this.isLink) {
-        let title = this.param["title"] || this.payload;
-        let a = document.createElement('a');
+        const title = this.param["title"] || this.payload;
+        const a = document.createElement('a');
         a.setAttribute('href', this.payload);
         a.setAttribute('rel', 'noopener noreferrer');
         a.addT(title);
diff --git a/dev/js/src/match/corpusByMatch.js b/dev/js/src/match/corpusByMatch.js
index 92d219a..6d5baa5 100644
--- a/dev/js/src/match/corpusByMatch.js
+++ b/dev/js/src/match/corpusByMatch.js
@@ -1,7 +1,9 @@
 define(['vc/fragment', 'util'], function (vcFragmentClass) {
+
   "use strict";
   
   return {
+
     /**
      * Constructor
      */
@@ -9,8 +11,10 @@
       return Object.create(this)._init(meta);
     },
 
+
     // Initialize corpusByMatch
     _init : function (meta) {
+      const t = this;
 
       // Meta is an element <dl />
       if (meta === undefined) {
@@ -21,10 +25,10 @@
       };
 
       // Collect the meta constraints
-      this._vc = {};
+      t._vc = {};
 
       // Remember the meta table
-      this._meta = meta;
+      t._meta = meta;
 
       // CorpusByMatch can be disabled per configuration.
       // This is necessary, as the feature won't work with
@@ -33,23 +37,24 @@
       // removed in future versions.
       // This will also require a change in matchinfo.scss
       if (KorAP.Conf && KorAP.Conf["CorpusByMatchDisabled"]) {
-        this._meta.classList.add("cbm-disabled");
-        return this;
+        t._meta.classList.add("cbm-disabled");
+        return t;
       };
 
-      this._meta.addEventListener(
-        "click", this.clickOnMeta.bind(this), false
+      t._meta.addEventListener(
+        "click", t.clickOnMeta.bind(t), false
       );
 
-      this._fragment = vcFragmentClass.create();      
+      t._fragment = vcFragmentClass.create();      
 
-      this._fragment.element().addEventListener(
-        "click", this.toVcBuilder.bind(this), true
+      t._fragment.element().addEventListener(
+        "click", t.toVcBuilder.bind(t), true
       );
 
-      return this;
+      return t;
     },
 
+
     /**
      * Join fragment with VC
      */
@@ -60,26 +65,24 @@
       if (this._fragment.isEmpty())
         return;
 
-      let vc = KorAP.vc;
+      const vc = KorAP.vc;
       if (!vc) {
         console.log("Global VC not established");
         return;
       };
 
-      
       for (const doc of this._fragment.documents()) {
         vc.addRequired(doc);
-        // console.log("Add " + doc.toQuery());
       };
 
-      if (!vc.isOpen()) {
+      if (!vc.isOpen())
         vc.open();
-      };
 
       // Scroll to top
       window.scrollTo(0, 0);
     },
 
+
     // Event handler for meta constraint creation
     clickOnMeta : function (e) {
       e.stopPropagation();
@@ -88,7 +91,7 @@
       };
 
       // Get event target
-      let target = e.target;
+      const target = e.target;
 
       let key, value, type;
 
@@ -114,45 +117,53 @@
 
       // Add or remove the constraint to the fragment
       if (key && value) {
+        const t = this;
         if (target.classList.contains("chosen")) {
           target.classList.remove("chosen");
-          this.remove(key, value);
+          t.remove(key, value);
         }
         else {
           target.classList.add("chosen");
-          this.add(key, value, type);
+          t.add(key, value, type);
         };
 
         // Check if the fragment is empty
         // If empty - hide!
-        if (!this._fragment.isEmpty()) {
-          this._meta.parentNode.insertBefore(
-            this._fragment.element(),
-            this._meta.nextSibling
+        if (!t._fragment.isEmpty()) {
+          t._meta.parentNode.insertBefore(
+            t._fragment.element(),
+            t._meta.nextSibling
           );
         }
 
         // Otherwise show!
         else {
-          this._meta.parentNode.removeChild(
-            this._fragment.element()
+          t._meta.parentNode.removeChild(
+            t._fragment.element()
           );
         };
       }
     },
 
-    // Add constraint
+    /**
+     * Add constraint to fragment
+     */
     add : function (key, value, type) {
       type = type.replace(/^type:/, '');
       this._fragment.add(key, value, type);
     },
 
-    // Remove constraint
+
+    /**
+     * Remove constraint from fragment
+     */
     remove : function (key, value) {
       this._fragment.remove(key, value);
     },
     
-    // Stringify annotation
+    /**
+     * Stringify fragment
+     */
     toQuery : function () {
       return this._fragment.toQuery();
     }
diff --git a/dev/js/src/match/infolayer.js b/dev/js/src/match/infolayer.js
index 82b9bd3..8d28286 100644
--- a/dev/js/src/match/infolayer.js
+++ b/dev/js/src/match/infolayer.js
@@ -3,7 +3,9 @@
  * about a match's layer annotation.
  */
 define(function () {
-  var _AvailableRE =
+  "use strict";
+
+  const _AvailableRE =
     new RegExp("^([^\/]+?)\/([^=]+?)(?:=(spans|rels|tokens))?$");
 
   return {
@@ -20,31 +22,34 @@
       return Object.create(this)._init(foundry, layer, type);
     },
 
+
     // Initialize Layer 
     _init : function (foundry, layer, type) {
       if (foundry === undefined)
 	      throw new Error("Missing parameters");
+
+      const t = this;
       
       if (layer === undefined) {
 	      if (_AvailableRE.exec(foundry)) {
-	        this.foundry = RegExp.$1;
-	        this.layer = RegExp.$2;
-	        this.type = RegExp.$3;
+	        t.foundry = RegExp.$1;
+	        t.layer = RegExp.$2;
+	        t.type = RegExp.$3;
 	      }
 	      else {
 	        throw new Error("Missing parameters");
 	      };
       }
       else {
-	      this.foundry = foundry;
-	      this.layer = layer;
-	      this.type = type;
+	      t.foundry = foundry;
+	      t.layer = layer;
+	      t.type = type;
       };
       
-      if (this.type === undefined)
-	      this.type = 'tokens';
+      if (t.type === undefined)
+	      t.type = 'tokens';
 
-      return this;
+      return t;
     }
   };
 });
diff --git a/dev/js/src/match/meta.js b/dev/js/src/match/meta.js
index 3cc7512..9c4dfb1 100644
--- a/dev/js/src/match/meta.js
+++ b/dev/js/src/match/meta.js
@@ -1,5 +1,7 @@
 define(['match/corpusByMatch','match/attachement','util'], function (cbmClass, attClass) {
 
+  "use strict";
+
   // Localization values
   const loc   = KorAP.Locale;
   loc.METADATA = loc.METADATA || 'Metadata';
@@ -13,16 +15,17 @@
       return Object.create(this)._init(match, fields);
     },
 
+
     /**
      * Initialize object
      */
     _init : function (match, fields) {
       this._match = match;
       this._fields = fields;
-      // this.opened = false;
       return this;
     },
 
+
     /**
      * Get match object
      */
@@ -30,6 +33,7 @@
       return this._match;
     },
 
+
     /**
      * Create match reference view.
      */
@@ -40,42 +44,40 @@
       if (this._fields === null)
         return;
 
-      var metaDL = document.createElement('dl');
+      const metaDL = document.createElement('dl');
       metaDL.classList.add("flex");
 
       this._element = metaDL;
 
-      let fields = this._fields;
+      const fields = this._fields;
 
       // Copy original array position to object
       // before sorting by key title
-      let posInMetaArray = {};
+      const posInMetaArray = {};
       fields.forEach((f,i) => posInMetaArray[f["key"]] = i);
 
-      
       // TODO: Meta fields should be separated
+
       // Sort all meta keys alphabetically
       Object.keys(posInMetaArray).sort().forEach(function(k) {
         let field = fields[posInMetaArray[k]]; // This is the object
 
+        let metaL, dt, metaDescr, metaDD, att;
+
         // Ignore internal IDs
         if (k !== "UID" &&
             k !== "corpusID" &&
             k !== "docID" &&
             k !== "textID" &&
-            /*
-              k !== "corpusSigle" &&
-              k !== "docSigle" &&
-            */
             k !== "layerInfos") {
 
-          const metaL = document.createElement('div');
+          metaL = document.createElement('div');
           
-          const dt = metaL.addE('dt');
+          dt = metaL.addE('dt');
           dt.addT(k);
           dt.setAttribute("title", k);
           
-          let metaDescr = field["value"];
+          metaDescr = field["value"];
           metaDD = metaL.addE('dd');
           metaDD.setAttribute('data-type', field["type"]);
 
@@ -83,7 +85,7 @@
         	  metaDD.classList.add("metakeyvalues");
             metaDescr.forEach(function(md) {
               if (field["type"] === 'type:attachement') {
-                let att = attClass.create(md);
+                att = attClass.create(md);
                 if (att)
         	        metaDD.addE('div').appendChild(att.inline());
               }
@@ -94,9 +96,9 @@
           }
           else{
             if (field["type"] === 'type:attachement') {
-              let att = attClass.create(field["value"]);
+              att = attClass.create(field["value"]);
               if (att)
-              metaDD.appendChild(att.inline());
+                metaDD.appendChild(att.inline());
             }
             else {
               metaDD.addT(field["value"]);
diff --git a/dev/js/src/match/querycreator.js b/dev/js/src/match/querycreator.js
index 99b0bc1..bfb6f09 100644
--- a/dev/js/src/match/querycreator.js
+++ b/dev/js/src/match/querycreator.js
@@ -19,7 +19,7 @@
   const loc = KorAP.Locale;
   loc.NEW_QUERY = loc.NEW_QUERY || 'New Query';
 
-  var esc = RegExp("[ \.\'\\\\\|\&]");
+  const esc = RegExp("[ \.\'\\\\\|\&]");
   
   function _getKeyValue (keyValue) {
     if (keyValue.match(esc) != null) {
@@ -27,13 +27,12 @@
     };
     return keyValue;
   };
-
   
   function _getAnnotation (prefix, target) {
 
     // Complex annotation
     if (target.childNodes.length > 1) {
-      var orGroup = [];
+      let orGroup = [];
 
       // Iterate over alternative annotations
       target.childNodes.forEach(function (item) {
@@ -70,39 +69,41 @@
       else if (!(matchTable instanceof Node))
         throw new Error('Requires element');
 
+      const t = this;
+
       // Collect the token sequence in an array
-      this._query = []
+      t._query = []
 
       // Get the match table
-      this._matchTable = matchTable;
+      t._matchTable = matchTable;
 
       // Listen on the match table
-      this._matchTable.addEventListener(
-        "click", this.clickOnAnno.bind(this), false
+      t._matchTable.addEventListener(
+        "click", t.clickOnAnno.bind(t), false
       );
 
       // Initialize element
-      this._element = document.createElement('p');
-      this._element.classList.add('query','fragment');
+      const e = t._element = document.createElement('p');
+      e.classList.add('query','fragment');
 
       // Prepend info text
-      this._element.addE('span').addT(loc.NEW_QUERY + ':');
+      e.addE('span').addT(loc.NEW_QUERY + ':');
 
       // Append query fragment part
-      this._queryFragment = this._element.addE('span');
+      t._queryFragment = e.addE('span');
 
       // Event when the query fragment is clicked
-      this._element.addEventListener('click', this.toQueryBar.bind(this), 1);
+      e.addEventListener('click', t.toQueryBar.bind(t), 1);
 
       // Get some basic information - see tutorial.js
       // TODO:
       //   It may be better to consultate a global object
       //   like KorAP.Hint, however ...
-      this._ql = document.getElementById("ql-field");
-	    this._q = document.getElementById("q-field")
+      t._ql = document.getElementById("ql-field");
+	    t._q = document.getElementById("q-field")
 
-      this._shown = false;
-      return this;
+      t._shown = false;
+      return t;
     },
 
 
@@ -113,7 +114,9 @@
       if (event.target !== event.currentTarget) {
 
         // Get target event
-        var target = event.target;
+        const target = event.target;
+
+        let head, foundry, layer, i, sib, annotation;
 
         if (target.tagName == 'TD') {
 
@@ -125,26 +128,23 @@
 
 
           // Check foundry and layer
-          var head    = target.parentNode.getElementsByTagName('th');
-          var foundry = head[0].innerText;
-          var layer   = head[1].innerText;
+          head    = target.parentNode.getElementsByTagName('th');
+          foundry = head[0].innerText;
+          layer   = head[1].innerText;
 
           // Check index position:
-          var i = -2;
-          var sib = target;
-          while((sib = sib.previousSibling) != null) {
+          i = -2;
+          sib = target;
+          while ((sib = sib.previousSibling) != null) {
             if (sib.nodeType === 1)
               i++;
           };
 
-
-          var prefix = foundry + '/' + layer + '=';
-          var annotation = '';
-
           // Get annotation value from cell
-          var annotation = _getAnnotation(prefix, target);
+          annotation = _getAnnotation(foundry + '/' + layer + '=', target);
 
           if (annotation !== '') {
+
             // Add term
             this.toggleInToken(target, i, annotation);
           };
@@ -152,6 +152,7 @@
 
         // The annotation is part of a key-value-pair
         else if (target.tagName == 'SPAN' || target.tagName == 'DIV') {
+
           if (target.innerText == '')
             return;
 
@@ -160,24 +161,21 @@
           };
 
           // Check foundry and layer
-          var parentCell = target.parentNode;
-          var head    = parentCell.parentNode.getElementsByTagName('th');
-          var foundry = head[0].innerText;
-          var layer   = head[1].innerText;
+          const parentCell = target.parentNode;
+          head    = parentCell.parentNode.getElementsByTagName('th');
+          foundry = head[0].innerText;
+          layer   = head[1].innerText;
 
           // Check index position of parent cell
-          var i = -2;
-          var sib = parentCell;
+          i = -2;
+          sib = parentCell;
           while((sib = sib.previousSibling) != null) {
             if (sib.nodeType === 1)
               i++;
           };
 
-          var prefix = foundry + '/' + layer + '=';
-          var annotation = '';
-
           // Get annotation value from cell
-          var annotation = _getAnnotation(prefix, target);
+          annotation = _getAnnotation(foundry + '/' + layer + '=', target);
 
           if (annotation !== '') {
 
@@ -197,8 +195,8 @@
               return;
             }
 
-            var i = -2;
-            var sib = target;
+            i = -2;
+            sib = target;
             while ((sib = sib.previousSibling) != null) {
               if (sib.nodeType === 1)
                 i++;
@@ -215,14 +213,14 @@
           else {
 
             // Check foundry and layer
-            var head    = target.parentNode.getElementsByTagName('th');
-            var foundry = head[0].innerText;
-            var layer   = head[1].innerText;
-            var prefix = foundry + '/' + layer + '=';
+            head    = target.parentNode.getElementsByTagName('th');
+            foundry = head[0].innerText;
+            layer   = head[1].innerText;
+            const prefix = foundry + '/' + layer + '=';
 
             // Iterate over all siblings
-            var i = 0;
-            var sib = target;
+            i = 0;
+            sib = target;
             while ((sib = sib.nextSibling) != null) {
               if (sib.nodeType !== 1 || sib.tagName === 'TH')
                 continue;
@@ -235,7 +233,7 @@
                 ).forEach(function(keyvaluepair){
 
                   // Get annotation value from cell
-                  var annotation = _getAnnotation(prefix, keyvaluepair);
+                  annotation = _getAnnotation(prefix, keyvaluepair);
 
                   if (annotation !== '') {
 
@@ -250,7 +248,7 @@
               else {
 
                 // Get annotation value from cell
-                var annotation = _getAnnotation(prefix, sib);
+                annotation = _getAnnotation(prefix, sib);
 
                 if (annotation !== '') {
 
@@ -269,10 +267,11 @@
       event.stopPropagation();
     },
 
+
     // Add term to token
     _addToToken : function (index, term) {
 
-      var token = this._query[index];
+      let token = this._query[index];
 
       // Initialize token
       if (token === undefined) {
@@ -295,18 +294,15 @@
 
     // Remove term from token
     _removeFromToken : function (index, term) {
-      var token = this._query[index];
+      let token = this._query[index];
 
       if (token === undefined)
         return;
 
       token.splice(token.indexOf(term), 1);
 
-      if (token.length > 0)
-        this._query[index] = token;
-      else
-        this._query[index] = undefined;
-
+      this._query[index] = token.length > 0 ? token : undefined;
+      
       this.show();
     },
 
@@ -326,56 +322,62 @@
     // Show annotation fragment
     show : function () {
 
-      var str = this.toString();
+      const t = this;
+      const str = t.toString();
+      const m = t._matchTable;
 
       // Fragment is empty
       if (str === '') {
 
         // Hide element
-        if (this._shown === true) {
-          this._matchTable.parentNode.removeChild(this._element);
-          this._shown = false;
+        if (t._shown === true) {
+          m.parentNode.removeChild(t._element);
+          t._shown = false;
         }
       }
 
       // Fragment is defined
       else {
 
-        if (this._shown === false) {
+        if (t._shown === false) {
 
           // Insert after
-          this._matchTable.parentNode.insertBefore(
-            this._element, this._matchTable.nextSibling
+          m.parentNode.insertBefore(
+            t._element, m.nextSibling
           );
-          this._shown = true;
+          t._shown = true;
         };
 
         // set value
-        this._queryFragment.innerText = str;
+        t._queryFragment.innerText = str;
       };
     },
 
+
     // Add term to token if not yet chosen, otherwise remove
     toggleInToken : function (node, index, term) {
-      if (node.classList.contains('chosen')) {
+      const cl = node.classList;
+      if (cl.contains('chosen')) {
         this._removeFromToken(index, term);
-        node.classList.remove('chosen');
+        cl.remove('chosen');
       }
       else {
         this._addToToken(index, term);
-        node.classList.add('chosen');
+        cl.add('chosen');
       };
     },
 
+
     // Stringify annotation
     toString : function () {
-      var str = '';
-      var distance = 0;
+      let str = '';
+      let distance = 0;
 
       // This needs to take undefined tokens into account, therefore
       // forEach() is not an option
-      for (var i = 0; i < this._query.length; i++) {
-        var token = this._query[i];
+      let token;
+      for (let i = 0; i < this._query.length; i++) {
+        token = this._query[i];
 
         // Token is defined
         if (token !== undefined) {
@@ -399,24 +401,26 @@
       return str;
     },
 
+
     // Add query fragment to query bar
     toQueryBar : function (e) {
+      const t = this;
 
-      if (this._ql === undefined || this._q === undefined || this._ql === null) {
+      if (t._ql === undefined || t._q === undefined || t._ql === null) {
         console.log('No query language object defined');
         return;
       };
 
-      // Set query language field
+      // Find query language field for Poliqarp
       const ql = Array.from(
-        this._ql.options
+        t._ql.options
       ).find(e => e.value == 'poliqarp');
 
       if (ql)
         ql.selected = true;
 
       // Insert to query bar
-      this._q.value = this.toString();
+      t._q.value = t.toString();
 
       // Scroll to top
       window.scrollTo(0, 0);
diff --git a/dev/js/src/match/table.js b/dev/js/src/match/table.js
index 92d4e5a..285e615 100644
--- a/dev/js/src/match/table.js
+++ b/dev/js/src/match/table.js
@@ -6,6 +6,8 @@
   'match/querycreator',
   "util"
 ], function (matchQueryCreator) {
+  "use strict";
+
   /*
    * TODO:
    *   Create base object for all matchinfo classes!
@@ -27,31 +29,35 @@
 
     // Initialize table based on snippet
     _init : function (snippet) {
+
       // Create html for traversal
-      var html = d.createElement("div");
+      const html = d.createElement("div");
+      const t = this;
       html.innerHTML = snippet;
       
-      this._pos = 0;
-      this._token = [];
-      this._mark = [];
-      this._markE = undefined;
-      this._cutted = [];
-      this._info = [];
-      this._foundry = {};
-      this._layer = {};
+      t._pos     = 0;
+      t._token   = [];
+      t._mark    = [];
+      t._markE   = undefined;
+      t._cutted  = [];
+      t._info    = [];
+      t._foundry = {};
+      t._layer   = {};
     
       // Parse the snippet
-      this._parse(html.childNodes, false);      
+      t._parse(html.childNodes, false);      
 
       html.innerHTML = '';
-      return this;
+      return t;
     },
 
+
     // TODO: Destroy match!
     destroy : function () {
       this._matchCreator = undefined;
     },
 
+
     /**
      * Length of the table (columns),
      * aka the number of tokens
@@ -74,6 +80,7 @@
       });
     },
     
+
     /**
      * Get the token in the snippet
      * At a given position.
@@ -86,6 +93,7 @@
       return this._token[pos];
     },
 
+
     /**
      * Get the annotation of a token
      * in the snippet based on the position,
@@ -105,18 +113,19 @@
 
       // Get all children
       children.forEach(function(c) {
+        const t = this;
 
         // Create object on position unless it exists
-        if (this._info[this._pos] === undefined) {
-          this._info[this._pos] = {};
+        if (t._info[t._pos] === undefined) {
+          t._info[t._pos] = {};
         };
 
         // Store at position in foundry/layer as array
-        var found = this._info[this._pos];
+        const found = t._info[t._pos];
 
         // Element with title
         if (c.nodeType === 1) {
-          var newMark = mark;
+          let newMark = mark;
 
           if (c.tagName === 'MARK') {
             newMark = true;
@@ -126,7 +135,7 @@
               _TermRE.exec(c.getAttribute("title"))) {
 
             // Fill position with info
-            var foundry, layer, value;
+            let foundry, layer, value;
             if (RegExp.$2) {
               foundry = RegExp.$1;
               layer   = RegExp.$2;
@@ -150,33 +159,33 @@
             }
 
             // Set foundry
-            if (this._foundry[foundry] === undefined)
-              this._foundry[foundry] = {};
-            this._foundry[foundry][layer] = 1;
+            if (t._foundry[foundry] === undefined)
+              t._foundry[foundry] = {};
+            t._foundry[foundry][layer] = 1;
 
             // Set layer
-            if (this._layer[layer] === undefined)
-              this._layer[layer] = {};
-            this._layer[layer][foundry] = 1;
+            if (t._layer[layer] === undefined)
+              t._layer[layer] = {};
+            t._layer[layer][foundry] = 1;
           }
 
           // The current position marks a cut
           else if (c.hasAttribute("class") && c.getAttribute("class") == "cutted") {
-            this._cutted.push(this._pos);
-            this._token[this._pos++] = "";            
+            t._cutted.push(t._pos);
+            t._token[t._pos++] = "";            
           }
 
           // depth search
           if (c.hasChildNodes())
-            this._parse(c.childNodes, newMark);
+            t._parse(c.childNodes, newMark);
         }
 
         // Leaf node
         // store string on position and go to next string
         else if (c.nodeType === 3) {
           if (c.nodeValue.match(/[a-z0-9\u25ae]/iu)) {
-            this._mark[this._pos] = mark ? true : false;
-            this._token[this._pos++] = c.nodeValue;
+            t._mark[t._pos] = mark ? true : false;
+            t._token[t._pos++] = c.nodeValue;
           };
         };
       }, this);
@@ -193,20 +202,20 @@
         return this._element;
 
       // First the legend table
-      var wrap = d.createElement('div');
+      const wrap = d.createElement('div');
 
-      var table = wrap.addE('table');
+      const table = wrap.addE('table');
 
       this._element = wrap;
 
       // Single row in head
-      var tr = table.addE('thead').addE('tr');
+      let tr = table.addE('thead').addE('tr');
 
-      var ah = KorAP.annotationHelper || { "getDesc" : function () {}};
-
+      const ah = KorAP.annotationHelper || { "getDesc" : function () {}};
+      
       // Add cell to row
-      var addCell = function (type, key, value) {        
-        var c = this.addE(type);
+      const addCell = function (type, key, value) {        
+        const c = this.addE(type);
 
         if (value === undefined)
           return c;
@@ -236,7 +245,7 @@
           c.addT(value);
 
           // Add tooltip
-          var anno = ah.getDesc(key, value);
+          const anno = ah.getDesc(key, value);
           if (anno)
             c.setAttribute("title", anno);
         };
@@ -252,8 +261,8 @@
 
       // Add tokens
       Object.keys(this._token).forEach(function(i) {
-        let surface = this.getToken(i);
-        var c = tr.addCell('th', undefined, surface);
+        const surface = this.getToken(i);
+        const c = tr.addCell('th', undefined, surface);
         if (this._mark[i]) {
           c.classList.add('mark');
           if (this._markE === undefined) {
@@ -270,13 +279,11 @@
         }
       }, this);
       
-      var tbody = table.addE('tbody');
-
-      var foundryList = Object.keys(this._foundry).sort();
+      const tbody = table.addE('tbody');
 
       let layerList, key, v, value, cell;
       
-      foundryList.forEach(function(foundry) {
+      Object.keys(this._foundry).sort().forEach(function(foundry) {
         let layerList =
             Object.keys(this._foundry[foundry]).sort();
 
diff --git a/dev/js/src/match/treearc.js b/dev/js/src/match/treearc.js
index afcd187..6e7c01c 100644
--- a/dev/js/src/match/treearc.js
+++ b/dev/js/src/match/treearc.js
@@ -19,53 +19,57 @@
     // Initialize the state of the object
     _init : function (snippet) {
 
+      const t = this;
+
       // Predefine some values
-      this._tokens  = [];
-      this._arcs    = [];
-      this._tokenElements = [];
-      this._y = 0;
-      this._currentInFocus = undefined;
+      t._tokens  = [];
+      t._arcs    = [];
+      t._tokenElements = [];
+      t._y = 0;
+      t._currentInFocus = undefined;
 
       // Some configurations
-      this.maxArc      = 200; // maximum height of the bezier control point
-      this.overlapDiff = 40;  // Difference on overlaps and minimum height for self-refernces
-      this.arcDiff     = 15;
-      this.anchorDiff  = 8;
-      this.anchorStart = 15;
-      this.tokenSep    = 30;
-      this.xPadding    = 10;
-      this.yPadding    = 5;
+      t.maxArc      = 200; // maximum height of the bezier control point
+      t.overlapDiff = 40;  // Difference on overlaps and minimum height for self-refernces
+      t.arcDiff     = 15;
+      t.anchorDiff  = 8;
+      t.anchorStart = 15;
+      t.tokenSep    = 30;
+      t.xPadding    = 10;
+      t.yPadding    = 5;
 
       // No snippet to process
       if (snippet == undefined || snippet == null)
-        return this;
+        return t;
 
       // Parse the snippet
-      var html = d.createElement("div");
+      const html = d.createElement("div");
       html.innerHTML = snippet;
 
       // Establish temporary parsing memory
-      this.temp = {
+      t.temp = {
         target : {}, // Remember the map id => pos        
         edges  : [], // Remember edge definitions
         pos    : 0   // Keep track of the current token position
       };
 
       // Start parsing from root
-      this._parse(0, html.childNodes, undefined);
+      t._parse(0, html.childNodes, undefined);
 
       // Establish edge list
-      var targetMap = this.temp['target'];
-      var edges = this.temp['edges'];
+      const targetMap = t.temp['target'];
+      const edges = t.temp['edges'];
 
+      let targetID, target, relation;
+      
       // Iterate over edge lists
       // TODO:
       //   Support spans for anchors!
       edges.forEach(function(edge) {
 
         // Check the target identifier
-        var targetID = edge.targetID;
-        var target = targetMap[targetID];
+        targetID = edge.targetID;
+        target = targetMap[targetID];
 
         if (target != undefined) {
 
@@ -78,7 +82,7 @@
           */
           
           // Add relation
-          var relation = {
+          relation = {
             start : [edge.srcStart, edge.srcEnd],
             end : target,
             direction : 'uni',
@@ -87,10 +91,10 @@
           // console.log(relation);
           this.addRel(relation);
         };
-      }, this);
+      }, t);
 
       // Reset parsing memory
-      this.temp = {};
+      delete t["temp"];
 
       return this;
     },
@@ -104,7 +108,7 @@
         // Element node
         if (c.nodeType == 1) {
 
-          var xmlid, target, start, end;
+          let xmlid, target, start, end;
 
           // Node is an identifier
           if (c.hasAttribute('xml:id')) {
@@ -136,7 +140,7 @@
             // Node is a relation
             // Stricter: c.getAttribute('xlink:show') == "none"
             else {
-              var label;
+              let label;
 
               // Get target id
               target = c.getAttribute('xlink:href').replace(/^#/, "");
@@ -146,6 +150,7 @@
               };
 
               // Remember the defined edge
+// WRONG!
               var edge = {
                 label    : label,
                 srcStart : this.temp['pos'],
@@ -173,7 +178,7 @@
 
             // Element already defined
             if (this.temp['target'][xmlid] !== undefined) {
-              var newtarget = this.temp['target'][xmlid];
+              const newtarget = this.temp['target'][xmlid];
               end = this.temp['pos'] - 1;
               newtarget[0] = start < newtarget[0] ? start : newtarget[0];
               newtarget[1] = end > newtarget[1] ? end : newtarget[1];
@@ -218,7 +223,9 @@
 
           // Check, if there is a non-whitespace token
           if (c.nodeValue !== undefined) {
-            var str = c.nodeValue.trim();
+
+            const str = c.nodeValue.trim();
+
             if (str !== undefined && str.length > 0) {
 
               // Add token to token list
@@ -255,21 +262,23 @@
       return d.createElementNS(svgNS, tag);
     },
 
+
     // Get bounding box - with workaround for text nodes
     _rect : function (node) {
       if (node.tagName == "tspan" && !navigator.userAgent.match(/Edge/)) {
-        var range = d.createRange();
+        const range = d.createRange();
         range.selectNode(node);
-        var rect = range.getBoundingClientRect();
+        const rect = range.getBoundingClientRect();
         range.detach();
         return rect;
       };
       return node.getBoundingClientRect();
     },
 
+
     // Returns the center point of the requesting token
     _tokenPoint : function (node) {
-	    var box = this._rect(node);
+	    const box = this._rect(node);
 	    return box.left + (box.width / 2);
     },
 
@@ -278,17 +287,22 @@
     _drawAnchor : function (anchor) {
 
       // Calculate the span of the first and last token, the anchor spans
-      var firstBox = this._rect(this._tokenElements[anchor.first]);
-      var lastBox  = this._rect(this._tokenElements[anchor.last]);
+      const firstBox = this._rect(this._tokenElements[anchor.first]);
+      const lastBox  = this._rect(this._tokenElements[anchor.last]);
 	
-      var startPos = firstBox.left - this.offsetLeft;
-      var endPos   = lastBox.right - this.offsetLeft;
+      const y = this._y + (anchor.overlaps * this.anchorDiff) - this.anchorStart;
+      const l = this._c('path');
       
-      var y = this._y + (anchor.overlaps * this.anchorDiff) - this.anchorStart;
-
-      var l = this._c('path');
 	    this._arcsElement.appendChild(l);
-	    var pathStr = "M " + startPos + "," + y + " L " + endPos + "," + y;
+
+      const pathStr = "M " +
+          (firstBox.left - this.offsetLeft) +
+          "," +
+          y +
+          " L " +
+          (lastBox.right - this.offsetLeft) +
+          "," + y;
+
       l.setAttribute("d", pathStr);
       l.setAttribute("class", "anchor");
       anchor.element = l;
@@ -301,61 +315,62 @@
     // Potentially needs a height parameter for stacks
     _drawArc : function (arc) {
 
-      var startPos, endPos;
-      var startY = this._y;
-      var endY = this._y;
+      const t = this;
+      let startPos, endPos;
+      let startY = this._y;
+      let endY = this._y;
 	
       if (arc.startAnchor !== undefined) {
-        startPos = this._tokenPoint(arc.startAnchor.element);
+        startPos = t._tokenPoint(arc.startAnchor.element);
         startY = arc.startAnchor.y;
       }
       else {
-        startPos = this._tokenPoint(this._tokenElements[arc.first]);
+        startPos = t._tokenPoint(t._tokenElements[arc.first]);
       };
 
       if (arc.endAnchor !== undefined) {
-        endPos = this._tokenPoint(arc.endAnchor.element)
+        endPos = t._tokenPoint(arc.endAnchor.element)
         endY = arc.endAnchor.y;
       }
       else {
-        endPos = this._tokenPoint(this._tokenElements[arc.last]);
+        endPos = t._tokenPoint(t._tokenElements[arc.last]);
       };
 
-      startPos -= this.offsetLeft;
-      endPos -= this.offsetLeft;
+      startPos -= t.offsetLeft;
+      endPos -= t.offsetLeft;
 
 	    // Special treatment for self-references
       var overlaps = arc.overlaps;
       if (startPos == endPos) {
-        startPos -= this.overlapDiff / 3;
-        endPos   += this.overlapDiff / 3;
+        startPos -= t.overlapDiff / 3;
+        endPos   += t.overlapDiff / 3;
         overlaps += .5;
       };
 
-      var g = this._c("g");
+      const g = t._c("g");
       g.setAttribute("class", "arc");
-      var p = g.appendChild(this._c("path"));
+      const p = g.appendChild(t._c("path"));
       p.setAttribute('class', 'edge');
       
       // Attach the new arc before drawing, so computed values are available
-      this._arcsElement.appendChild(g);
+      t._arcsElement.appendChild(g);
 
       // Create arc
-      var middle = Math.abs(endPos - startPos) / 2;
+      let middle = Math.abs(endPos - startPos) / 2;
 
       // TODO:
       //   take the number of tokens into account!
-      var cHeight = this.arcDiff + (overlaps * this.overlapDiff) + (middle / 2);
+      let cHeight = t.arcDiff + (overlaps * t.overlapDiff) + (middle / 2);
 
       // Respect the maximum height
-      cHeight = cHeight < this.maxArc ? cHeight : this.maxArc;
+      cHeight = cHeight < t.maxArc ? cHeight : t.maxArc;
 
       var x = Math.min(startPos, endPos);
 
       //var controlY = (startY + endY - cHeight);
-      var controlY = (endY - cHeight);
+      let controlY = (endY - cHeight);
       
-      var arcE = "M "+ startPos + "," + startY +
+      const arcE = "M "+ startPos + "," + startY +
           " C " + startPos + "," + controlY +
           " " + endPos + "," + controlY +
           " " + endPos + "," + endY;
@@ -379,53 +394,58 @@
        * of course simplified to symmetric arcs ...
        */
       // Interpolate one side of the control polygon
-      var middleY = (((startY + controlY) / 2) + controlY) / 2;
+      let middleY = (((startY + controlY) / 2) + controlY) / 2;
 
       // Create a boxed label
-      var label = this._c("g");
+      const label = this._c("g");
       label.setAttribute("class", "label");
-      this._labelsElement.appendChild(label);
+      t._labelsElement.appendChild(label);
 
       // Set arc reference
       label.arcRef = g;
 
-      var that = this;
+      const that = t;
       label.addEventListener('mouseenter', function () {
         that.inFocus(this);
       });
 
-      var labelE = label.appendChild(this._c("text"));
+      const labelE = label.appendChild(t._c("text"));
       labelE.setAttribute("x", x + middle);
       labelE.setAttribute("y", middleY + 3);
       labelE.setAttribute("text-anchor", "middle");
-      var textNode = d.createTextNode(arc.label);
+      const textNode = d.createTextNode(arc.label);
       labelE.appendChild(textNode);
 
-      var labelBox   = labelE.getBBox();
+      const labelBox   = labelE.getBBox();
 
+      /*
       if (!labelBox)
         console.log("----");
+      */
       
-      var textWidth  = labelBox.width; // labelE.getComputedTextLength();
-      var textHeight = labelBox.height; // labelE.getComputedTextLength();
+      const textWidth  = labelBox.width; // labelE.getComputedTextLength();
+      const textHeight = labelBox.height; // labelE.getComputedTextLength();
 
       // Add box with padding to left and right
-      var labelR = label.insertBefore(this._c("rect"), labelE);
-      var boxWidth = textWidth + 2 * this.xPadding;
+      const labelR = label.insertBefore(t._c("rect"), labelE);
+      const boxWidth = textWidth + 2 * t.xPadding;
       labelR.setAttribute("x", x + middle - (boxWidth / 2));
       labelR.setAttribute("ry", 5);
-      labelR.setAttribute("y", labelBox.y - this.yPadding);
+      labelR.setAttribute("y", labelBox.y - t.yPadding);
       labelR.setAttribute("width", boxWidth);
-      labelR.setAttribute("height", textHeight + 2 * this.yPadding);
+      labelR.setAttribute("height", textHeight + 2 * t.yPadding);
     },
 
-    // Get the svg element
+
+    /**
+     * Get the svg element
+     */
     element : function () {
       if (this._element !== undefined)
         return this._element;
 
       // Create svg
-      var svg = this._c("svg");
+      const svg = this._c("svg");
 
       window.addEventListener("resize", function () {
         // TODO:
@@ -436,13 +456,14 @@
       }.bind(this));
 
       // Define marker arrows
-      var defs = svg.appendChild(this._c("defs"));
-      var marker = defs.appendChild(this._c("marker"));
+      const defs = svg.appendChild(this._c("defs"));
+      const marker = defs.appendChild(this._c("marker"));
       marker.setAttribute("refX", 9);
       marker.setAttribute("id", "arr");
       marker.setAttribute("orient", "auto-start-reverse");
       marker.setAttribute("markerUnits","userSpaceOnUse");
-      var arrow = this._c("path");
+
+      const arrow = this._c("path");
       arrow.setAttribute("transform", "scale(0.8)");
       arrow.setAttribute("d", "M 0,-5 0,5 10,0 Z");
       marker.appendChild(arrow);
@@ -451,6 +472,7 @@
       return this._element;
     },
 
+
     // Add a relation with a start, an end,
     // a direction value and an optional label text
     addRel : function (rel) {
@@ -468,7 +490,7 @@
 
     // Move label and arc in focus
     inFocus : function (element) {
-      var cif;
+      let cif;
 
       if (this._currentInFocus) {
 
@@ -488,6 +510,7 @@
       cif.arcRef.classList.add('infocus');
     },
     
+
     /*
      * All arcs need to be sorted before shown,
      * to avoid nesting.
@@ -498,7 +521,7 @@
       //   Keep in mind that the arcs may have long anchors!
       //   1. Iterate over all arcs
       //   2. Sort all multi
-      var anchors = {};
+      let anchors = {};
       
       // 1. Sort by length
       // 2. Tag all spans with the number of overlaps before
@@ -510,7 +533,7 @@
       //       reorder
 
       // Normalize start and end
-      var sortedArcs = this._arcs.map(function (v) {
+      const sortedArcs = this._arcs.map(function (v) {
 
         // Check for long anchors
         if (v.start instanceof Array) {
@@ -521,16 +544,18 @@
 
           else {
           
-            var middle = Math.ceil(Math.abs(v.start[1] - v.start[0]) / 2) + v.start[0];
+            const middle = Math.ceil(Math.abs(v.start[1] - v.start[0]) / 2) + v.start[0];
 
             // Calculate signature to avoid multiple anchors
-            var anchorSig = "#" + v.start[0] + "_" + v.start[1];
+            let anchorSig = "#" + v.start[0] + "_" + v.start[1];
+
+            // Reverse signature
             if (v.start[0] > v.start[1]) {
               anchorSig = "#" + v.start[1] + "_" + v.start[0];
             };
             
             // Check if the anchor already exist
-            var anchor = anchors[anchorSig];
+            let anchor = anchors[anchorSig];
             if (anchor === undefined) {
               anchor = {
                 "first":   v.start[0],
@@ -538,7 +563,6 @@
                 "length" : v.start[1] - v.start[0]
               };
               anchors[anchorSig] = anchor;
-              // anchors.push(v.startAnchor);
             };
 
             v.startAnchor = anchor;
@@ -556,10 +580,12 @@
 
           else {
 
-            var middle = Math.abs(v.end[0] - v.end[1]) + v.end[0];
+            const middle = Math.abs(v.end[0] - v.end[1]) + v.end[0];
 
             // Calculate signature to avoid multiple anchors
-            var anchorSig = "#" + v.end[0] + "_" + v.end[1];
+            let anchorSig = "#" + v.end[0] + "_" + v.end[1];
+
+            // Reverse signature
             if (v.end[0] > v.end[1]) {
               anchorSig = "#" + v.end[1] + "_" + v.end[0];
             };
@@ -573,27 +599,24 @@
                 "length" : v.end[1] - v.end[0]
               };
               anchors[anchorSig] = anchor;
-              // anchors.push(v.startAnchor);
             };
             
             v.endAnchor = anchor;
 
             // Add to anchors list
-            // anchors.push(v.endAnchor);
             v.end = middle;
           };
         };
 
         v.first = v.start;
-        v.last = v.end;
+        v.last  = v.end;
 
         // calculate the arch length
         if (v.start < v.end) {
           v.length = v.end - v.start;
         }
+
         else {
-          // v.first = v.end;
-          // v.last = v.start;
           v.length = v.start - v.end;
         };
 
@@ -613,19 +636,20 @@
       this._sortedAnchors = lengthSort(Object.values(anchors), true);
     },
 
+
     /**
      * Center the viewport of the canvas
      * TODO:
-     *   This is identical to tree
+     *   This is identical to treehierarchy
      */
     center : function () {
       if (this._element === undefined)
        return;
 
-      var treeDiv = this._element.parentNode;
+      const treeDiv = this._element.parentNode;
 
-      var cWidth = parseFloat(window.getComputedStyle(this._element).width);
-      var treeWidth = parseFloat(window.getComputedStyle(treeDiv).width);
+      const cWidth = parseFloat(window.getComputedStyle(this._element).width);
+      const treeWidth = parseFloat(window.getComputedStyle(treeDiv).width);
       // Reposition:
       if (cWidth > treeWidth) {
        var scrollValue = (cWidth - treeWidth) / 2;
@@ -636,37 +660,38 @@
 
     // Show the element
     show : function () {
-      var svg = this._element;
-      var height = this.maxArc;
+      const t = this;
+      const svg = this._element;
+      const height = this.maxArc;
 
       // Delete old group
       if (svg.getElementsByTagName("g")[0] !== undefined) {
-        var group = svg.getElementsByTagName("g")[0];
-        svg.removeChild(group);
-        this._tokenElements = [];
+        svg.removeChild(
+          svg.getElementsByTagName("g")[0]
+        );
+        t._tokenElements = [];
       };
 
-      var g = svg.appendChild(this._c("g"));
+      const g = svg.appendChild(t._c("g"));
 
       // Draw token list
-      var text = g.appendChild(this._c("text"));
+      const text = g.appendChild(t._c("text"));
       text.setAttribute('class', 'leaf');
       text.setAttribute("text-anchor", "start");
       text.setAttribute("y", height);
 
       // Calculate the start position
-      this._y = height - (this.anchorStart);
+      t._y = height - (t.anchorStart);
 
       // Introduce some prepending whitespace (yeah - I know ...)
-      var ws = text.appendChild(this._c("tspan"));
+      const ws = text.appendChild(t._c("tspan"));
       ws.appendChild(d.createTextNode('\u00A0'));
       ws.style.textAnchor = "start";
       
-      var lastRight = 0;
-      this._tokens.forEach(function(node_i) {
+      t._tokens.forEach(function(node_i) {
         // Append svg
         // var x = text.appendChild(this._c("text"));
-        var tspan = text.appendChild(this._c("tspan"));
+        const tspan = text.appendChild(this._c("tspan"));
         tspan.appendChild(d.createTextNode(node_i));
         tspan.setAttribute("text-anchor", "middle");
         
@@ -674,38 +699,36 @@
 
         // Add whitespace!
         tspan.setAttribute("dx", this.tokenSep);
-      }, this);
+      }, t);
 
       // Get some global position data that may change on resize
-      var globalBoundingBox = this._rect(g);
-      this.offsetLeft = globalBoundingBox.left;
+      t.offsetLeft = t._rect(g).left;
 
       // The group of arcs
-      var arcs = g.appendChild(this._c("g"));
-      this._arcsElement = arcs;
+      const arcs = g.appendChild(t._c("g"));
+      t._arcsElement = arcs;
       arcs.classList.add("arcs");
 
-      var labels = g.appendChild(this._c("g"));
-      this._labelsElement = labels;
+      const labels = g.appendChild(t._c("g"));
+      t._labelsElement = labels;
       labels.classList.add("labels");
 
       // Sort arcs if not sorted yet
-      if (this._sortedArcs === undefined)
-        this._sortArcs();
+      if (t._sortedArcs === undefined)
+        t._sortArcs();
 
       // 1. Draw all anchors
-      this._sortedAnchors.forEach(
-        i => this._drawAnchor(i)
+      t._sortedAnchors.forEach(
+        i => t._drawAnchor(i)
       );
 
       // 2. Draw all arcs
-      this._sortedArcs.forEach(
-        i => this._drawArc(i)
+      t._sortedArcs.forEach(
+        i => t._drawArc(i)
       );
 
       // Resize the svg with some reasonable margins
-      var width = this._rect(text).width;
-      svg.setAttribute("width", width + 20);
+      svg.setAttribute("width", t._rect(text).width + 20);
       svg.setAttribute("height", height + 20);
       svg.setAttribute("class", "relTree");
     }
@@ -720,15 +743,16 @@
      * e.g. if identical start or endpoints mean overlap or not.
      */
     
-    var stack = [];
+    let stack = [];
 
     // Iterate over all definitions
     list.forEach(function(current) {
 
       // Check the stack order
-      var overlaps = 0;
-      for (var j = (stack.length - 1); j >= 0; j--) {
-        var check = stack[j];
+      let overlaps = 0;
+      let check;
+      for (let j = (stack.length - 1); j >= 0; j--) {
+        check = stack[j];
 
         // (a..(b..b)..a)
         if (current.first <= check.first && current.last >= check.last) {
diff --git a/dev/js/src/match/treehierarchy.js b/dev/js/src/match/treehierarchy.js
index 9fc2480..e54ef29 100644
--- a/dev/js/src/match/treehierarchy.js
+++ b/dev/js/src/match/treehierarchy.js
@@ -16,10 +16,10 @@
 
   // Create path for node connections 
   function _line (src, target) {
-    var x1 = src.x,
-        y1 = src.y,
-        x2 = target.x,
-        y2 = target.y - target.height / 2;
+    const x1 = src.x,
+          y1 = src.y,
+          x2 = target.x,
+          y2 = target.y - target.height / 2;
 
     // c 0,0 -10,0
     return 'M ' + x1 + ',' + y1 + ' ' + 
@@ -36,7 +36,7 @@
      */
     create : function (snippet) {
       return Object.create(this).
-       _init(snippet);
+        _init(snippet);
     },
 
 
@@ -45,16 +45,18 @@
       this._next = new Number(0);
       
       // Create html for traversal
-      var html = d.createElement("div");
+      let html = d.createElement("div");
       html.innerHTML = snippet;
-      var g = new dagre.graphlib.Graph({
-       "directed" : true 
+
+      const g = new dagre.graphlib.Graph({
+        "directed" : true 
       });
+
       g.setGraph({
-       "nodesep" : 35,
-       "ranksep" : 15,
-       "marginx" : 40,
-       "marginy" : 10
+        "nodesep" : 35,
+        "ranksep" : 15,
+        "marginx" : 40,
+        "marginy" : 10
       });
       g.setDefaultEdgeLabel({});
 
@@ -62,8 +64,8 @@
       
       // This is a new root
       this._addNode(
-       this._next++,
-       { "class" : "root" }
+        this._next++,
+        { "class" : "root" }
       );
       
       // Parse nodes from root
@@ -71,7 +73,7 @@
 
       // Root node has only one child - remove
       if (g.outEdges(0).length === 1)
-       g.removeNode(0);
+        g.removeNode(0);
 
       html = undefined;
       return this;
@@ -82,6 +84,7 @@
       return d.createElementNS(svgNS, tag);
     },
     
+
     /**
      * The number of nodes in the tree.
      */
@@ -89,6 +92,7 @@
       return this._next;
     },
 
+
     // Add new node to graph
     _addNode : function (id, obj) {
       obj["width"]  = WIDTH;
@@ -97,81 +101,84 @@
       return obj;
     },
     
+
     // Add new edge to graph
     _addEdge : function (src, target) {
       this._graph.setEdge(src, target);
     },
     
+
     // Remove foundry and layer for labels
     _clean : function (title) {
       return title.replace(_TermRE, "$3");
     },
 
+    
     // Parse the snippet
     _parse : function (parent, children, mark) {
       children.forEach(function(c) {
 
-       // Element node
-       if (c.nodeType == 1) {
+        // Element node
+        if (c.nodeType == 1) {
 
-         // Get title from html
-         if (c.getAttribute("title")) {
-           var title = this._clean(c.getAttribute("title"));
+          // Get title from html
+          if (c.getAttribute("title")) {
 
-           // Add child node
-           var id = this._next++;
+            // Add child node
+            const id = this._next++;
 
-           var obj = this._addNode(id, {
-             "class" : "middle",
-             "label" : title
-           });
+            const obj = this._addNode(id, {
+              "class" : "middle",
+              "label" : this._clean(c.getAttribute("title"))
+            });
             
             if (mark !== undefined) {
               obj.class += ' mark';
             };
             
-           this._addEdge(parent, id);
+            this._addEdge(parent, id);
 
-           // Check for next level
-           if (c.hasChildNodes())
-             this._parse(id, c.childNodes, mark);
-         }
+            // Check for next level
+            if (c.hasChildNodes())
+              this._parse(id, c.childNodes, mark);
+          }
 
-         // Step further
-         else if (c.hasChildNodes()) {
+          // Step further
+          else if (c.hasChildNodes()) {
 
-            if (c.tagName === 'MARK') {
-             this._parse(parent, c.childNodes, true);
-            }
-            else {
-             this._parse(parent, c.childNodes, mark);
-            };
+            this._parse(
+              parent,
+              c.childNodes,
+              c.tagName === 'MARK' ? true : mark
+            );
           };
-       }
+        }
 
-       // Text node
-       else if (c.nodeType == 3)
+        // Text node
+        else if (c.nodeType == 3)
 
-         if (c.nodeValue.match(/[-a-z0-9]/i)) {
+          if (c.nodeValue.match(/[-a-z0-9]/i)) {
+            
+            // Add child node
+            const id = this._next++;
+            this._addNode(id, {
+              "class" : "leaf",
+              "label" : c.nodeValue
+            });
 
-           // Add child node
-           var id = this._next++;
-           this._addNode(id, {
-             "class" : "leaf",
-             "label" : c.nodeValue
-           });
-
-           this._addEdge(parent, id);
-         };
+            this._addEdge(parent, id);
+          };
       }, this);
       return this;
     },
 
+
     // Dummy method to be compatible with relTree
     show : function () {
       return;
     },
 
+
     /**
      * Center the viewport of the canvas
      * TODO:
@@ -179,16 +186,15 @@
      */
     center : function () {
       if (this._element === undefined)
-       return;
+        return;
 
-      var treeDiv = this._element.parentNode;
+      const treeDiv = this._element.parentNode;
+      const cWidth = parseFloat(window.getComputedStyle(this._element).width);
+      const treeWidth = parseFloat(window.getComputedStyle(treeDiv).width);
 
-      var cWidth = parseFloat(window.getComputedStyle(this._element).width);
-      var treeWidth = parseFloat(window.getComputedStyle(treeDiv).width);
       // Reposition:
       if (cWidth > treeWidth) {
-       var scrollValue = (cWidth - treeWidth) / 2;
-       treeDiv.scrollLeft = scrollValue;
+        treeDiv.scrollLeft = (cWidth - treeWidth) / 2;
       };
     },
 
@@ -199,11 +205,12 @@
     toBase64 : function () {
 
       // First clone element
-      var svgWrapper = d.createElement('div')
+      const svgWrapper = d.createElement('div')
       svgWrapper.innerHTML = this.element().outerHTML;
-      var svg = svgWrapper.firstChild;
 
-      var style = this._c('style');
+      const svg = svgWrapper.firstChild;
+      const style = this._c('style');
+
       svg.getElementsByTagName('defs')[0].appendChild(style);
 
       style.innerHTML = 
@@ -217,45 +224,50 @@
       return btoa(unescape(encodeURIComponent(svg.outerHTML)).replace(/&nbsp;/g, ' '));
     },
     
+
     /**
      * Get the dom element of the tree view.
      */
     element : function () {
+
       if (this._element !== undefined)
-       return this._element;
+        return this._element;
 
-      var g = this._graph;
-
+      const g = this._graph;
       dagre.layout(g);
       
-      var canvas = this._c('svg');
+      const canvas = this._c('svg');
       this._element = canvas;
-      var that = this;
 
       canvas.appendChild(this._c('defs'));
-      
-      var height = g.graph().height;
 
       // Create edges
+      const that = this;
+
+      let src, target, p;
+
       g.edges().forEach(
         function (e) {
-          var src = g.node(e.v);
-          var target = g.node(e.w);
-          var p = that._c('path');
+          src = g.node(e.v);
+          target = g.node(e.w);
+          p = that._c('path');
           p.setAttributeNS(null, "d", _line(src, target));
           p.classList.add('edge');
           canvas.appendChild(p);
-        });
+        }
+      );
+      
+      let height = g.graph().height;
 
       // Create nodes
       g.nodes().forEach(
         function (v) {
           v = g.node(v);
-          var group = that._c('g');
+          const group = that._c('g');
           group.setAttribute('class', v.class);
           
           // Add node box
-          var rect = group.appendChild(that._c('rect'));
+          const rect = group.appendChild(that._c('rect'));
           rect.setAttribute('x', v.x - v.width / 2);
           rect.setAttribute('y', v.y - v.height / 2);
           rect.setAttribute('rx', 5);
@@ -271,18 +283,18 @@
 
           // Add label
           if (v.label !== undefined) {
-            var text = group.appendChild(that._c('text'));
-            var y = v.y - v.height / 2;
+            const text = group.appendChild(that._c('text'));
+            let y = v.y - v.height / 2;
             text.setAttribute('y', y);
             text.setAttribute(
               'transform',
               'translate(' + v.width/2 + ',' + ((v.height / 2) + 5) + ')'
             );
 
-            var vLabel = v.label.replace(/&nbsp;/g, " ")
-                .replace(/&amp;/g, '&')
-                .replace(/&lt;/g, '<')
-                .replace(/&gt;/g, '>');
+            const vLabel = v.label.replace(/&nbsp;/g, " ")
+                  .replace(/&amp;/g, '&')
+                  .replace(/&lt;/g, '<')
+                  .replace(/&gt;/g, '>');
             
             if (v.class === "leaf") {
               text.setAttribute('title', vLabel);
@@ -295,10 +307,12 @@
 
                 tspan = that._c('tspan');
                 tspan.appendChild(d.createTextNode(p));
+
                 if (n !== 0)
                   tspan.setAttribute('dy', LINEHEIGHT + 'pt');
                 else
                   n = 1;
+
                 tspan.setAttribute('x', v.x - v.width / 2);
                 y += LINEHEIGHT;
                 text.appendChild(tspan);
@@ -311,7 +325,7 @@
                 height = y;
             }
             else {
-              var tspan = that._c('tspan');
+              const tspan = that._c('tspan');
               tspan.appendChild(d.createTextNode(vLabel));
               tspan.setAttribute('x', v.x - v.width / 2);
               text.appendChild(tspan);
@@ -325,9 +339,9 @@
       canvas.setAttribute('height', height);
       return this._element;
     },
-
+    
     downloadLink : function () {
-      var a = d.createElement('a');
+      const a = d.createElement('a');
       a.setAttribute('href-lang', 'image/svg+xml');
       a.setAttribute('href', 'data:image/svg+xml;base64,' + this.toBase64());
       a.setAttribute('download', 'tree.svg');
diff --git a/dev/js/src/match/treeitem.js b/dev/js/src/match/treeitem.js
index d99165a..422f3d7 100644
--- a/dev/js/src/match/treeitem.js
+++ b/dev/js/src/match/treeitem.js
@@ -27,6 +27,7 @@
       return this._content;
     },
     
+
     /**
      * The foundry attribute of the menu item.
      */
@@ -34,6 +35,7 @@
       return this._foundry;
     },
 
+
     /**
      * The layer attribute of the menu item.
      */
@@ -41,6 +43,7 @@
       return this._layer;
     },
 
+
     /**
      * The type attribute of the menu item.
      * Is either "spans" or "rels".
@@ -49,30 +52,35 @@
       return this._type;
     },
     
+
     /**
      * Override click action of the menu item.
      */
     onclick : function (e) {
-      var menu = this.menu();
+      const menu = this.menu();
       menu.hide();
       e.halt();
+
       if (menu.panel() !== undefined) {
 	      menu.panel().addTree(this._foundry, this._layer, this._type);
       };
     },
 
+
     // Initialize tree menu item.
     _init : function (params) {
       if (params[0] === undefined)
 	      throw new Error("Missing parameters");
 
-      this._name    = params[0];
-      this._foundry = params[1];
-      this._layer   = params[2];
-      this._type    = params[3];
-      this._content = document.createTextNode(this._name);
-      this._lcField = ' ' + this.content().textContent.toLowerCase();
-      return this;
+      const t = this;
+
+      t._name    = params[0];
+      t._foundry = params[1];
+      t._layer   = params[2];
+      t._type    = params[3];
+      t._content = document.createTextNode(t._name);
+      t._lcField = ' ' + t.content().textContent.toLowerCase();
+      return t;
     }
   };
 });