Regarding `bind` in constructor for class methods

tobindornottobind.js

// Bind class methods that would be call externally by when executing `new Foo()`
// context to `this` for the current class context will be lost when assigning the method to another object 
// e.g

// Binding a method as an instance property
class Bar {
  constructor() {
    //this.bar = this.bar.bind(this); // <-- this line is required when obj reference is being passed around such that the context of `this` is lost
    this.counter = 0
  }
  
  bar() {
    this.counter++
    console.log('bar', this);
  }
  
  that() {
    this.bar()
  }
}

var bartop = new Bar()
const barsss = bartop.bar 
console.log('barss', barsss); // runtime error due to `counter` is not defined when this.bar = this.bar.bind(this); is commented out

// Cases when .bind(this) is needed

function passFnByRef(fnRef) {
  fnRef() // when you need to pass a function as an argument and execute it at a point
  // if you did not do a `.bind(this)` in the constructor method when you call the function, 
  // context of `this` will be `undefined` or `window`. And methods call with `this.` will complained
  // `undefined`
} 

// Applies to ES7 class fields / ES6 class / ES5 prototypal inheritiance