Handle inner this inside callback function in strict mode

Question

I got stuck with problem TS2683 while using webix(5.4.0) + typescript(3.1.1) in strict mode.

($$('DATE') as webix.ui.datepicker)attachEvent('onChange', function() {
      let val:any = this.getValue() // or let val = ... without any
      // this:this??? () = > not suit for me, btw
      ...
}

error is:

'this' implicity has type 'any' because it doesn't have a type annotation.

I've read How to access the correct `this` inside a callback? But it seems, everything's about handling outer this, moreover I need to declare inner this type. So what should I do?

score 0 · Accepted Answer · answered Oct 11 '18 at 14:12

You need to add a type annotation to let the compiler know the type of this

($$('DATE') as webix.ui.datepicker).attachEvent('onChange', function(this:webix.ui.datepicker) {
    let val:any = this.getValue()    
});

Ideally the attachEvent method should have specified the type of this in the callback type but since it does not you need to specify it manually.

Handle inner this inside callback function in strict mode

1 Answers1