typescript callback from promise and access 'this'

Question

Got difficult to figure this. Failed to call this.doA() from the callback of external Promise.

class A {
    private _startCallback;

    // register callbacks
    constructor({startCallback}) {
        this._startCallback = startCallback;
    }
   load() {
       // A external promise.
       HelloPromise.get({callbackA: myCallback}).then(...)
   }

   private myCallback() {
      // FAILED to Call doA
      this.doA() 
   }
   private doA() {
   }
}

Possible duplicate of [TypeScript "this" scoping issue when called in jquery callback](http://stackoverflow.com/questions/20627138/typescript-this-scoping-issue-when-called-in-jquery-callback) — Aleksey L., Aug 21 '16 at 13:59
Or any of dozens if not hundreds of other similar questions, which can be found with a google search for something like "javascript method callback this:". — , Aug 21 '16 at 14:01

Nitzan Tomer · Answer 1 · 2016-08-21T14:00:34.100

1

The context of this is different when the method myCallback is executed.

You have two options:

(1) Using an arrow function:

HelloPromise.get({ callbackA: () => { this.myCallback(); } }).then(...)

(2) Using the Function.prototype.bind function:

HelloPromise.get({ callbackA: this.myCallback.bind(this) }).then(...)

edited Aug 21 '16 at 14:00

answered Aug 21 '16 at 13:57

Nitzan Tomer

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Well, in any case it has to be `this.myCallback`, right? – Aug 21 '16 at 13:59
@torazaburo Indeed! missed that part, thanks, I changed the answer – Nitzan Tomer Aug 21 '16 at 14:01

typescript callback from promise and access 'this'

1 Answers1