lahmatiy

Similar solutions with very different execution times. What's the reason? Why solution #1 is too slow?

Hint: access to .length property and to variables is not an issue.

Based on a real case in CSSTree

Node v6.11.3

N	Solution #1	Solution #2

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//
// Case 1
//

var a = [];
var t = performance.now();

for (var i = 0; i < 10000; i++)
  a.push(new Promise(function(){}));
  

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// Unique with use object
function uniqueObject(array) {
    var hash = Object.create(null);
    var result = [];
    var value;

    for (var i = 0; i < array.length; i++) {
        value = array[i];
        if (!hash[value]) {
            hash[value] = true;

lahmatiy

var events = require('basis.event');
var resolveValue = require('basis.data').resolveValue;

module.exports = function createBlockClass(BaseClass, ext) {
    return BaseClass.subclass(ext, {
        visible: true,
        visibleRA_: null,
        emit_visibleChanged: events.create('visibleChanged'),
        // value could be a function or binding-bridge instance; any other converts to bool
        setVisible: function(value) {

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var csso = require('csso');

function splitByScope(css) {
    var scopes = {};

    csso.walk(csso.parse(css), function(node) {
        if (node.type === 'Class') {
            var className = node.name;
            var scopeId = className.replace(/^([^_]+)_.+/, '$1'); // scopeId is block name

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// react 0.14-rc1
var Zoo = React.createClass({
  render: function() {
    return <div>Giraffe name: <input ref="giraffe" /></div>;
  },
  showName: function() {
    // Previously: var input = this.refs.giraffe.getDOMNode();
    var input = this.refs.giraffe;
    alert(input.value);
  }

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  basis.require('basis.event');
  basis.require('basis.data');


  var datasetComputeFunctions = {};

  basis.data.AbstractDataset.extend({
   /**
    * @param {string|Array.<string>=} events

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basis.require('basis.data.value');
basis.require('basis.dom');

var DOM = basis.dom;
var BindValue = basis.data.value.BindValue;

var DOM_INSERT_HANDLER = function(value){
  DOM.insert(DOM.clear(this), value);
};

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var ids = String(
  this.req.param('id') ||
  this.req.param('ids')
).match(/(\d+)/g);

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basis.require('basis.entity');
basis.require('basis.data.index');

// create type with single field, that used for EntitySet
var Item = basis.entity.createType('SomeType', {
  value: Number
});

// main Entity type
var DemoType = basis.entity.createType('DemoType', {