08-this-is-hard.js

/* 
    THIS IS HARD
    
    This section is about the keyword "this" in JavaScript.
    It behaves very differently from class-based object-oriented langauges
    like Java and C#.

    We'll be using the function hello() throughout this section.
*/

function hello() {
    return this + ' says hello';
}


let task1 = hello();
// Look at the first test below - what does hello() output?

/* 
    We want our function to say 'Erik says hello'
    by manipulating the function context (the value of "this" inside the function)
    use call() to set the function context!
*/

let task2;

// Achieve the same as above, but with using apply instead of call
let task3;

/*
    Imagine not having to use "call" og "apply" every time, but rather
    create a new function with a certain context. Whenever this new function is called,
    it calls the old function with the desired context. Sounds great?!
    Function.prototype.bind lets us do exactly this.
*/

// Use bind to create a new version of "hello()" that' always bound to "Kygo"

let boundHello;

/*
    Now lets implement bind() manually, by creating a wrapper function
    that always calls the inner function with a certain context when called.
    It should work like this: 
    let boundFunc = bind(unboundFunc, context);
    i.e: let boundHello = bind(hello, 'Kygo');
*/

function bind(func, context) {}

// If you want to learn more about function invocation in
// JavaScript, here's some recommended reading:
// http://yehudakatz.com/2011/08/11/understanding-javascript-function-invocation-and-this/

test('This is hard', function() {
    equal(task1, '[object Window] says hello', 'This is supposed to pass');
    equal(task2, 'Erik says hello');
    equal(task3, 'Erik says hello');
    equal(boundHello && boundHello(), 'Kygo says hello');
    equal(homeboundHello && homeboundHello(), 'Kygo says hello');
});