ecmascript-5

The ECMAScript specification for Math.pow has the following peculiar rule: If x < 0 and x is finite and y is finite and y is not an integer, the result is NaN. ( http://es5.github.com/#x15.8.2.13 ) As a result Math.pow(-8, 1 / 3) gives NaN rather than -2 What is the reason for this rule? Is there some sort of broader computer science or IEEEish reason for this rule, or is it just a choice TC39/Eich made once upon a time? Update Thanks to Amadan's exchanges with me, I think I understand the reasoning now. I would like to expand upon our discussion for the sake of posterity. Let's take the

I'm reading about JavaScript closures . I'm familiar with Execution Contexts , how the Lexical Environment is maintained, and very familiar with Lexical Scoping . I want to know how closures in JavaScript are created and maintained . Sometimes it's hard for me to grasp such important concepts without knowing how it is actually doing it. I know that, according to Wikipedia, a closure is is a function or reference to a function together with a referencing environment—a table storing a reference to each of the non-local variables (also called free variables) of that function. But my question is,

I'm having trouble understanding why, in strict mode, a syntax error occurs when delete is used on an unqualified identifier. In most cases, it makes sense... if you are declaring variables in the usual way with the var keyword, and then trying to use delete on them, in non-strict mode it would silently fail, so it makes sense for strict mode to fail with an error in those cases. However, there are cases where you can't delete identifiers that are qualified: (function() { // "use strict"; var obj = Object.create({}, { bloop: { configurable: false } }); delete obj.bloop; // throws TypeError in

If you're using the module pattern and have something like this: (function () { "use strict"; // this function is strict... }()); and compile the code using the Google Closure Compiler, the "use strict"; directive will not make it into the compiled file. So how do you prevent the Closure Compiler from removing the ES5/strict directive? (Note that I don't want to use the other mode of enforcing ES5/strict mode, which is to simply add the "use strict"; to the first line of the compiled file. I want to use the module pattern as described here .) This isn't the greatest answer, but as far as I can

So Safari and Chrome have started in their betas to implement some ES5 stuff. For instance Object.create is in them. Do any of you know if there is a website that shows the progress made in the browsers? ATM i need to use Object.freeze, and wanted to see which browsers (if any) supported that yet. Tihauan Here's an up to date list for major engines: http://kangax.github.com/es5-compat-table/ 来源： https://stackoverflow.com/questions/2280115/ecmascript-5-browser-implementation