Why can I not access this JS function ? Undefined is not a function?

Question

This is probably pretty stupid but it's been bugging me for a little while now. Trying to get something going with AngularJS and this is killing me.

Within a callback I have something like so:

var xyz = {
  "modA"  : null,
  "modB"  : null,
  "modC"  : null
}

I then attach some methods as well...

xyz.setModA = function(elementId) {

  var someConfig = {};
  // attach some kind of event callback on stateChange
  someConfig.events.onStateChange = this.helper;

  this.modA = new someObject(someConfig);      

}

xyz.setModC = function(vars) {
    ....
}

xyz.helper = function(event) {
  ....
  this.setModC(vars);
}

When the state of the modA object we instantiated changes then the onStateChange event occurs and correctly fires the xyz.helper method I have but then I instantly get an Uncaught TypeError: undefined is not a function ? For some reason it's not seeing the setModC method now when the event fires?

Wouldn't this.setModC = 'something'; in xyz.helper blow away your setModC method? — Keen
– Keen, Commented May 30, 2014 at 17:02
@Cory Well seen. It's not current OP's bug but it could be the next one... — Denys Séguret
– Denys Séguret, Commented May 30, 2014 at 17:05
@Cory well seen indeed! Helper should've had this.setModC(cars); as the call which my real code actually has. — skålfyfan
– skålfyfan, Commented May 30, 2014 at 17:26

Denys Séguret · Accepted Answer · 2014-05-30 16:59:58Z

6

The context (this) in the event handler isn't the desired object.

To ensure the right context, change

someConfig.events.onStateChange = this.helper;

to

someConfig.events.onStateChange = this.helper.bind(this);

answered May 30, 2014 at 16:59

Denys Séguret

384k90 gold badges813 silver badges780 bronze badges

Sign up to request clarification or add additional context in comments.

Collectives™ on Stack Overflow

Why can I not access this JS function ? Undefined is not a function?

1 Answer 1

Comments

Your Answer

Hot Network Questions

Collectives™ on Stack Overflow

1 Answer 1

Comments

Your Answer

Sign up or log in

Post as a guest

Related