javascript - Why use a closure instead of a prototype?

[Sgraffite]

I see this all the time, but I've never understand the reason other than maybe habit? That's my only guess.

For example:

function Foo() {
	var temp = 1;
	function bar() {
		console.log(temp);
	}
	function barPlusOne() {
		console.log(temp + 1);
	}
}

Foo.prototype = {
	temp: 1,
	bar: function(){
		console.log(this.temp);
	},
	barPlusOne: function() {
		console.log(this.temp + 1);
	}
}

I could definitely be missing something, but I've always written it the latter way.

 

[Ken g6]

Hm, looks like you're doing something with closures and OOP? I've never done that.

The only time I've used a closure is to pass function parameters to a callback.

 

[purbeast0]

pretty good explanation with some more links to other information:

http://stackoverflow.com/questions/3564238/object-oriented-javascript-with-prototypes-vs-closures

 

[TheRyuu]

Also check out Optimizing JavaScript[1] from some Google folks.

[1] https://developers.google.com/speed/articles/optimizing-javascript

 

[Sgraffite]

I meant the use of closures for encapsulating data structures instead of using object prototypes to do so. Anonymous functions for callbacks aren't really closures as far as I am aware.

 

[Cogman]

I meant the use of closures for encapsulating data structures instead of using object prototypes to do so. Anonymous functions for callbacks aren't really closures as far as I am aware.

They are

https://en.wikipedia.org/wiki/Closure_(computer_programming)

Pretty much the only two requirements for something to be a closure are that it must be passable and it must include current scope at its declaration.

Pretty much every function in javascript, anonymous or otherwise, is a closure because of the javascript scope rules.