understand javascript arrow function and this

arrow.js

/*!
 * understand `arrow function` and `this`
 * see also https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Functions/Arrow_functions
 */

var id = 'global';

var o = {
  id: 'o',

  echoThisId() {
    console.log(this.id);
  },

  echoThisIdDelay() {
    setTimeout(this.echoThisId, 1000);
  },

  echoThisIdDelay2() {
    setTimeout(function () {
      this.echoThisId();
    }, 1000);
  },

  echoThisIdDelay3() {
    setTimeout(() => this.echoThisId(), 1000);
  }
}

o.echoThisId() // 'o'
//o.echoThisIdDelay(); // 'global'
// o.echoThisIdDelay2();  // Uncaught TypeError: this.echoThisId is not a function
o.echoThisIdDelay3(); // 'o'

this script works natively in current Chrome release(V47).