No, you can’t disable strict mode per function. It’s important to understand that strict mode works lexically; meaning — it affects function declaration, not execution. Any function declared within strict code becomes a strict function itself. But not any function called from within strict code is necessarily strict: (function(sloppy) { “use strict”; function strict() { … Read more
There are several things that you can’t emulate from the ECMAScript 5 Object.create method on an ECMAScript 3 environment. As you saw, the properties argument will give you problems since in E3-based implementations there is no way to change the property attributes. The Object.defineProperty method as @Raynos mentioned, works on IE8, but partially, it can … Read more
It appears to be O(n) in V8 (chrome, node.js) at least: > var hash = {} > , c = 0; > > var s = +new Date();Object.keys(hash);console.log(+new Date() – s); 0 > for(var i=0; i<100000; i++, c++){ hash[c] = 1; } > var s = +new Date();Object.keys(hash);console.log(+new Date() – s); 26 > for(var i=0; … Read more
Your cryptic part isn’t all that cryptic if you rewrite it a little: [][”] [] will be coerced into a string because it isn’t an integer, so you’re looking for a property of [] with the name ” (an empty string). You’ll just get undefined, as there is no property with that name. As for … Read more
Where does the specification say that values of the Object type behave differently than primitives? Is it only that primitives are immutable, and objects are mutable? Yes, it bascially boils down to the mutability of objects, and the identity of objects. Actually, this is not even specified anywhere, it is just assumed as a given … Read more
UPDATE from 2021 Despite this being the accepted answer, 10 years of experience has taught me this isn’t the best idea. Pretty much anything you can do avoid polluting the global scope is a very very good thing. Original answer below, for posterity, and because stack overflow will not let me delete an accepted answer. … Read more
I’ll give this a try. Note that I’m not affiliated with ECMA and have no visibility into their decision-making process, so I cannot definitively say why they have or have not done anything. However, I’ll state my assumptions and take my best shot. 1. Why add a for…of construct in the first place? JavaScript already … Read more
The difference between let and const is that once you bind a value/object to a variable using const, you can’t reassign to that variable. In other words Example: const something = {}; something = 10; // Error. let somethingElse = {}; somethingElse = 1000; // This is fine. The question details claim that this is … Read more
Yes, catch clauses indeed have their own Lexical Environments. Check out what happens when it is evaluated: It creates a new one (deriving from the current one) and binds the exception-identifier to it. When executing the catch block, the current Execution Context’s LexicalEnvironment is switched to the new one, while the VariableEnvironment(“whose environment record holds … Read more
There are so many answers around there but people always get confused. I know this because I got confused once a while ago. After some time, I grasped the concepts. Bind object/function manually in order to play with state or props inside the function and to avoid scope-related issues Not exactly true. You don’t need … Read more