Nested function parameters and 'this' context in Javascript

Question

I'm trying to create a chain of function calls using two objects.

I've added comments in the code to describe what I'm trying to do:

function Huh(parentContext) {
this.parentContext = parentContext;
this.check = function() {
    console.log(parentContext);
}
this.DoWork = function(successFunc) {
    console.log('Huh.DoWork');
    successFunc('yay');     
};}

function Thing() {  
this.nextSuccess = function(e) {    
    console.log('nextSuccess ' + e);
};

this.success = function(e) {
    console.log('success!! ' + e);

    var h = new Huh(this);  // It looks like 'this' doesn't mean the Thing context any more. ?!?!
    //h.check();    
    h.DoWork(this.nextSuccess);  // THIS BREAKS. 
};

this.fail = function() {
    console.log('fail');
};

this.firstBit = function(successFunc, failFunc) {
    var h = new Huh(this);  
    //h.check();        
    h.DoWork(this.success);     
};

// start with this function
this.Go = function() {
    this.firstBit(this.success, this.fail);
};}

It all breaks when I try to create a second instance of Huh in Thing.success.

I try to pass in this.nextSuccess however it seems like the 'this' context isn't the same anymore.

Please help.

When you're using nested functions, please try to reflect this in the indentation. It makes it MUCH easier to read. — Skilldrick
– Skilldrick, Commented Jun 29, 2010 at 9:46
Sorry about that. I tried to get the indentation working but the code block just kept breaking. — sf.
– sf., Commented Jun 29, 2010 at 9:57

Skilldrick · Accepted Answer · 2010-06-29 09:43:03Z

7

At the start of your Thing function, put var that = this;. You can then access the Thing this using that.

answered Jun 29, 2010 at 9:43

Skilldrick

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1 Comment

sf. Over a year ago

Thanks for that. I don't suppose you could explain why it fails in the original code please? I'd love to get a better understanding :)

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