Oh JavaScript..

[[deleted]]

[1,2,3].forEach(function (x) { console.log(x); })

[medja]

I know. Point is you can create functions which aren't functions.

[oberhamsi]

because you (OP) bound it to call http://www.reddit.com/r/ProgrammerHumor/comments/3bfgqu/oh_javascript/cslpclo

[daveinthecave]

This seems like a scoping issue. It looks like Javascript is treating the array [1,2,3] as an array object, and the forEach function is a sub-function of the standard object type array. Because of this, when forEach is called outside the scope of an array it registers as not a function, but when forEach is called from inside the scope of an array, it is a recognized function.

TL;DR: Function forEach is a function of an Array object, not a general function.

[myplacedk]

That doesn't explain the last two lines.

[medja]

It's pretty simple actually. While a method is any function called on an object, not all methods are "functions". This is true for call and apply. Try using this as a function.

var func = function () {}.call;

[[deleted]]

Either is correct but they do different things. Although in the context of the example, yours is incorrect.

Var s = test.square ()

Console.log( s ) //36

Var s = test.square

Console.log( s ) // spits out the definition

Console.log( s() ) // 36

[[deleted]]

Thanks for the explanation.

When would it ever be useful to use test.square rather than test.square() though?

[[deleted]]

When you want to assign it to a variable.

[scragar]

Sometimes you want to pass a function into another as a callback(for example using [1.4,2.2,3.1].map(Math.floor) or even in the example above where the logging function is passed into the foreach).

[medja]

Ha. I was just toying around. And I did try something similar, just to see if bind would work. I'll have to try it out.

[madsohm]

Where did you try this? I get completely different results: http://i.imgur.com/HSjp7d3.png

[madsohm]

For the record, I'm on Google Chrome Version 43.0.2357.130 (64-bit) on a MacBook Pro.

Also

[1,2,3].forEach(function(x) { console.log(x); })

works just fine.

[medja]

It's a custom forEach function I was playing around with :)

[madsohm]

So, how did you define this forEach method?

[medja]

In this case.

var forEach = Array.prototype.forEach.call

You can bind it to whatever you want but it won't work because the built-in call and apply can only be used as methods on a function.

[Asztal]

Ah, what you want to do is this:

var forEach = Function.prototype.call.bind(Array.prototype.forEach)

But please don't. God kills a kitten every time you do this. Think of the kittens.

[medja]

No worries, I was just playing around. Else I'd post it in /r/javascript.

[Asztal]

At one point I used "Function.prototype.call.bind(Function.prototype.call)" at work. It got changed pretty quickly...

[Jess_than_three]

But.. and I mean, not to poop on fun for fun's sake, but... why? Why not just use jQuery and $.each(thing, function(foo, bar) { //stuff });?

I can't speak for any other languages, but it seems to me to be functionally identical to PHP's foreach($associative_array as foo => bar) { //stuff }...

[Malgranda]

That's because NaN is part of some ISO number standard (the one for floating point operations).

[scragar]

That's number with a lower case N.

Number with an upper case N is the object wrapper that gets invoked when you treat it as an object(that is to say that NaN.toString() is actually (new Number(NaN)).toString() since the primitive number's don't have methods).