angularjs - Cannot access class variable -

i started using typescript angularjs. have written simple class responsible drag , drop behavior (or in future). right in handledragend function when access canvas element error

cannot read property of undefined

below code - if tell me doing wrong grateful.

class toolbox { private canvas;  constructor(canvas) {     this.canvas = canvas;      $(".beacon").draggable({         helper: 'clone',         cursor: 'pointer',         start: this.handledragstart,         stop: this.handledragend     });         }  handledragstart() {     console.log('drag started!'); }  handledragend() {                   var pointer = this.canvas.getpointer(event.e);      console.log('drag end!');       return; } } 

since class methods defined on toolbox.prototype, value of this getting lost when pass in methods directly.

change:

start: this.handledragstart, stop: this.handledragend 

to:

start: () => this.handledragstart(), stop: () => this.handledragend() 

that preserve value of this calling methods on instance.