Demonstration of how bind() works in JavaScript

bind.js

/** 
 *
 * Incorrect Context 
 *
 */
class Greeter {

	constructor(name) {
		this.name = name;
	}

	greet(event) {
		console.log('Hello ' + this.name); // undefined
	}
}

const greeter = new Greeter('Shaun');

var a = document.createElement('button');
a.id = 'greet-button';
a.innerHTML = 'Say Hello';
a.onclick = greeter.greet;

document.body.appendChild(a);

/** 
 *
 * Correct Context 
 *
 */
class Greeter {

	constructor(name) {
		this.name = name;
		this.greet = this.greet.bind(this);
	}

	greet(event) {
		console.log('Hello ' + this.name); // 'Shaun'
	}
}

const greeter = new Greeter('Shaun');

var a = document.createElement('button');
a.id = 'greet-button';
a.innerHTML = 'Say Hello';
a.onclick = greeter.greet;

document.body.appendChild(a);