| Leo Repp | 58b9f11 | 2021-11-22 11:57:47 +0100 | [diff] [blame^] | 1 | 'use strict'; |
| 2 | |
| 3 | // there's 3 implementations written in increasing order of efficiency |
| 4 | |
| 5 | // 1 - no Set type is defined |
| 6 | function uniqNoSet(arr) { |
| 7 | var ret = []; |
| 8 | |
| 9 | for (var i = 0; i < arr.length; i++) { |
| 10 | if (ret.indexOf(arr[i]) === -1) { |
| 11 | ret.push(arr[i]); |
| 12 | } |
| 13 | } |
| 14 | |
| 15 | return ret; |
| 16 | } |
| 17 | |
| 18 | // 2 - a simple Set type is defined |
| 19 | function uniqSet(arr) { |
| 20 | var seen = new Set(); |
| 21 | return arr.filter(function (el) { |
| 22 | if (!seen.has(el)) { |
| 23 | seen.add(el); |
| 24 | return true; |
| 25 | } |
| 26 | |
| 27 | return false; |
| 28 | }); |
| 29 | } |
| 30 | |
| 31 | // 3 - a standard Set type is defined and it has a forEach method |
| 32 | function uniqSetWithForEach(arr) { |
| 33 | var ret = []; |
| 34 | |
| 35 | (new Set(arr)).forEach(function (el) { |
| 36 | ret.push(el); |
| 37 | }); |
| 38 | |
| 39 | return ret; |
| 40 | } |
| 41 | |
| 42 | // V8 currently has a broken implementation |
| 43 | // https://github.com/joyent/node/issues/8449 |
| 44 | function doesForEachActuallyWork() { |
| 45 | var ret = false; |
| 46 | |
| 47 | (new Set([true])).forEach(function (el) { |
| 48 | ret = el; |
| 49 | }); |
| 50 | |
| 51 | return ret === true; |
| 52 | } |
| 53 | |
| 54 | if ('Set' in global) { |
| 55 | if (typeof Set.prototype.forEach === 'function' && doesForEachActuallyWork()) { |
| 56 | module.exports = uniqSetWithForEach; |
| 57 | } else { |
| 58 | module.exports = uniqSet; |
| 59 | } |
| 60 | } else { |
| 61 | module.exports = uniqNoSet; |
| 62 | } |