JavaScript Memory Management (Info)

Question

What I am trying to work out is whether nullifying is always necessary. As I am having a few issues with Chrome. Say I have this code.

function MyClass() {}
MyClass.prototype.MyFunction = function() {
 this.data = "foo";
}
var c = new MyClass();
c.MyFunction();

Now once that function is called it should be allowed to be GC but should the end of the function have this.data = null. Should this also be standard.

• James Allardice: That code will throw a TypeError. Did you mean to instantiate MyClass?
• Yoshi: here's a helpful article: ibm.com/developerworks/library/wa-memleak
• Sam_Benne: Yeah I was writing the code in here and forgot to add that.

Answer 1

Your code will not work. You should first create an instance of your class:

var c = new MyClass();
c.MyFunction();

because MyFunction is instance function.

Otherwise there's also delete operator (reference and an indepth analysis), that is used to remove object members (but not objects themselves). Objects can therefore be garbage collected when there's no way to reference them any more, so

c = undefined;

should convince Javascript to garbage collect this object instance and release memory resources taken by it.

It is different if your object instance is instantiated this way:

c = new MyClass();
c.MyFunction();
delete c; // success

because c is this time a member of global (window) and can therefore be deleted from it.

• Sam_Benne: My main issue is that I cannot remove the main class.
• Robert Koritnik: @Sam_Benne: Class or instance of your class?
• Sam_Benne: Instance. Its a "Single Page App" So I need to keep the main instance but I can clear other smaller ones which I do.
• Robert Koritnik: @Sam_Benne: So what's the problem then? Why and when would you want to clear the main instance?
• Sam_Benne: I haven't got a problem what I was trying to find out is whether the GC would clean out the vars that are generated in the function when it is not in use.