In underscore.js you can use like, _.extend(firstObj, secondObj); In jQuery, you can use, $.extend({},firstObj,secondObj); In pure javascipt, you can merge n number of objects by using this function: function mergeObjects() { var resObj = {}; for(var i=0; i < arguments.length; i += 1) { var obj = arguments[i], keys = Object.keys(obj); for(var j=0; j < … Read more
TL;DR Just omit the type tag, if you don’t care about old browsers. ECMAScript is a language specification standardized by ECMA International as ECMA-262 and ISO/IEC 16262. JavaScript is a programming language that implements this specification. ECMAScript exists in several editions. The latest edition is the 6th (in 2016), but most JavaScript implementations are only … Read more
The main difference between #4 and all other cases is that the first time when you use a closure as a constructor is always quite expensive. It is always handled in V8 runtime (not in generated code) and transition between compiled JS code and C++ runtime is quite expensive. Subsequent allocations usually are handled in … Read more
Octal literals are not allowed because disallowing them discourages programmers from using leading zeros as padding in a script. For example, look at the following snippet: var eight = 0008, nine = 00009, ten = 000010, eleven = 011; console.log(eight, nine, ten, eleven); Seems harmless enough, right? We programmers with OCD just want to align … Read more
The question you linked, its answers, and the references it gives list a bunch of reasons for using strict mode. Let me call out just one of them: The Horror of Implicit Globals¹ Non-strict code: function foo(a) { var myvar; myar = a * 4; // … return myvar; } Now, this code: console.log(foo(2)); …should … Read more
Preface A couple of quick points before we get into the meat of this: All modern desktop browsers support use strict… No, not at all. IE8 is a fairly modern browser (not anymore, in 2015), and IE9 is a quite fairly modern browser. Neither of them supports strict mode (IE9 supports parts of it). IE8 … Read more
The language reference uses abstract terms because JavaScript environments can vary widely. In the browser, a window (a frame, a window opened with window.open(), or just a plain browser tab) is a realm. A web worker is a different kind of realm than a window, but it’s a realm. Same goes for service workers. It’s … Read more
Update: See my compatibility table. Original response: None as of now. Raphael Speyer was working on Mozilla implementation for Rhino during this summer, and afaik, their implementation is pretty close to completion. I know (based on info from ES-discuss list) that Microsoft is planning to include some of ES5 features into upcoming versions of IE … Read more
Update: strict mode is now supported in the compiler. Just use –language_in=ECMASCRIPT5_STRICT. References: http://code.google.com/p/closure-compiler/issues/detail?id=69 http://code.google.com/p/closure-compiler/source/detail?r=873 http://code.google.com/p/closure-compiler/source/detail?r=1114
Check here: https://developer.mozilla.org/en-US/docs/JavaScript/Reference/Global_Objects/Array/map Mozilla has supplied an Array.map polyfill for unsupported browsers if (!Array.prototype.map) { Array.prototype.map = function(callback, thisArg) { var T, A, k; if (this == null) { throw new TypeError(” this is null or not defined”); } // 1. Let O be the result of calling ToObject passing the |this| value as the … Read more