mirror of https://github.com/thangisme/notes.git
63 lines
1.1 KiB
JavaScript
63 lines
1.1 KiB
JavaScript
'use strict';
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// there's 3 implementations written in increasing order of efficiency
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// 1 - no Set type is defined
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function uniqNoSet(arr) {
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var ret = [];
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for (var i = 0; i < arr.length; i++) {
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if (ret.indexOf(arr[i]) === -1) {
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ret.push(arr[i]);
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}
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}
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return ret;
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}
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// 2 - a simple Set type is defined
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function uniqSet(arr) {
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var seen = new Set();
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return arr.filter(function (el) {
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if (!seen.has(el)) {
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seen.add(el);
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return true;
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}
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return false;
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});
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}
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// 3 - a standard Set type is defined and it has a forEach method
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function uniqSetWithForEach(arr) {
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var ret = [];
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(new Set(arr)).forEach(function (el) {
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ret.push(el);
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});
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return ret;
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}
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// V8 currently has a broken implementation
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// https://github.com/joyent/node/issues/8449
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function doesForEachActuallyWork() {
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var ret = false;
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(new Set([true])).forEach(function (el) {
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ret = el;
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});
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return ret === true;
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}
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if ('Set' in global) {
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if (typeof Set.prototype.forEach === 'function' && doesForEachActuallyWork()) {
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module.exports = uniqSetWithForEach;
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} else {
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module.exports = uniqSet;
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}
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} else {
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module.exports = uniqNoSet;
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}
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