14_this.md

this

Global Scope

Non-strict mode

console.log(this); // Window Object

Strict mode

"use strict";
console.log(this); // Window Object

Function Scope

Non-strict mode

function test(){
    console.log(this);
}
test();// Window object

Strict mode

"use strict";
function test(){
    console.log(this);
}
test();// undefined

• In strict mode, the default value of this is undefined. Use strict mode STOP this object being the global object becuase most of the time, we don't want this to be a global object.

In Object (this is called in a function of Object)

Non-strict mode

var person = {
    name: "Hiroko",
    getName: function(){
        console.log(this.name);
    },
    prop:{
        name: "Grace",
        getName: function(){
            console.log(this.name);
        }  
    }
}

person.getName();//hiroko
person.prop.getName(); //Grace

Strict mode

"use strict";
var person = {
    name: "Hiroko",
    getName: function(){
        console.log(this.name);
    },
    prop:{
        name: "Grace",
        getName: function(){
            console.log(this.name);
        }  
    }
}

person.getName();//hiroko
person.prop.getName(); //Grace

In Object but not directly called.

Non-strict mode

var name = 'Tom';
var person = {
    name: "Hiroko",
    getName: function(){
        console.log(this.name);
    },
};

var func = person.getName;
func();//Tom

Strict mode

"use strict";
var name = 'Tom';
var person = {
    name: "Hiroko",
    getName: function(){
        console.log(this.name);
    },
};

var func = person.getName;
func(); //Cannot read property 'name' of undefined

In Object with a nested function

Non-strict mode

var person = {
    name: "Hiroko",
    getName: function(){
        console.log(this.name);
        function checkNexted(){
        	console.log(this);
        }
        checkNexted();
    },
};

person.getName();
//Hiroko
// Window

Strict mode

"use strict";
var person = {
    name: "Hiroko",
    getName: function(){
        console.log(this.name);
        function checkNexted(){
        	console.log(this);
        }
        checkNexted();
    },
};

person.getName();
// Hiroko
// undefined

Summary

Excercise

Non strict mode

var fullname = 'John Doe';
var obj = {
   fullname: 'Colin Ihrig',
   prop: {
      fullname: 'Aurelio De Rosa',
      getFullname: function() {
         return this.fullname;
      }
   }
};

console.log(obj.prop.getFullname());// Aurelio De Rosa
var test = obj.prop.getFullname; 
console.log(test()); //John Doe

Strict mode

"use strict";
var fullname = 'John Doe';
var obj = {
   fullname: 'Colin Ihrig',
   prop: {
      fullname: 'Aurelio De Rosa',
      getFullname: function() {
         return this.fullname;
      }
   }
};

console.log(obj.prop.getFullname());// Aurelio De Rosa
var test = obj.prop.getFullname; 
console.log(test()); //undefined