`this` keyword

console.log(this); // window (global scope)

console.log('\n\n ****************************** \n\n');

this.hafeez = 'Hafeez Syed'; // `this.hafeez` will be `window.hafeez` because this -> window

console.log(this.hafeez); // Hafeez Syed
console.log(window.hafeez); // Hafeez Syed
console.log(hafeez); // Hafeez Syed

console.log('\n\n ****************************** \n\n');

function checkThis() {
    console.log(this); // window as function `checkThis` is called from the golbal scope
}

checkThis();

console.log('\n\n ****************************** \n\n');

var hafeez = {
    checkMe: function() {
        console.log(this);
    },
    checkThis: function() {
        function fullName() {
            this.fullName = 'Hafeez Syed';
            console.log(this); // window, `this` here is pointing to `window` object not `hafeez` object
        }

        fullName();
        console.log(this.fullName); // undefined because, here `this` is pointing to Object 'hafeez'
        console.log(window.fullName); // Hafeez Syed,        
    },
    checkThat: function() {
        var that = this;
        function fullName() {
            that.fullName = 'Hafeez Syed';
            console.log(that); // Object {}, unlike `checkThis` example, this` here is pointing to `hafeez` object not `window` object because `this` has been assigned to another variable `that`
        }

        fullName();
        console.log(that.fullName); // Hafeez Syed, because here `that` is pointing to Object 'hafeez'
        console.log(window.fullName); // Hafeez Syed,        
    }
}

hafeez.checkMe(); // Object {}, as function `checkMe` is called by the Object `hafeez`

console.log('\n\n ****************************** \n\n');

var checkFunc = hafeez.checkMe;

checkFunc(); // window, because function `checkFunc` is called from the global scope

console.log('\n\n ****************************** \n\n');

hafeez.checkThis();

console.log('\n\n ****************************** \n\n');

hafeez.checkThat();

console.log('\n\n ****************************** \n\n');