Correct syntax needed for bind() on 'this' object using class

Mon 2018.09.17

ref MDN bind(): https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Function/bind

Goal:
1) Retrieve the internal contents of an instantiated class
2) Modify the internal value and retain through subsequent retrieval attempts

The MDN example works using the Json object notation form. When I attempt to use a class however, I'm greeted with either function not found or undefined

class TestBind {

  constructor() {
//    var vX = -1;
    var vX = 23;
  }
 
  getX() { 
    return this.vX; 
  }

  setX( obj ) {
    this.vX = obj;
  }

}
exports = TestBind;

The constructor seems to ignore the initial default assignment - why not -1

var tb = new TestBind();
var g = tb.getX;
print g

Undefined

Then if I use a setter, then it's not clear if the constructor initialized correctly

var tb = new TestBind();
tb.setX = 42;
var g = tb.getX;
print g

=42

If I use the () notation - so which is correct, without the () or using the () ?
How can function getX() not be found when it is clearly defined?

var tb = new TestBind();
var g = tb.getX();
print g

Uncaught Error: Function "getX" not found!

Following the example from MDN, and applying to this class

var tb = new TestBind();
//tb.setX = 42;
//var g = tb.getX;
var g = tb.getX();
print g
var bg = g.bind(tb);
print bg

var bg = g.bind(tb);
Uncaught Error: Cannot read property 'bind' of undefined

VERSION 1v99

1 Attachment

• codeBindExample20180917.js