this binding

foo.js

function foo() {
    console.log( this.a );
}
 
var a = 2;
 
foo(); // 2

foo2.js

function foo() {
    "use strict";
 
    console.log( this.a );
}
 
var a = 2;
 
foo();  // TypeError: `this` is `undefined

foo3.js

function foo() {
    console.log( this.a );
}

var obj = {
    a: 2,
    foo: foo
};

var bar = obj.foo; // function reference/alias!

var a = "oops, global"; // `a` also property on global object

bar(); // "oops, global"

foo4.js

function foo() {
    console.log( this.a );
}

var obj = {
    a: 2,
    foo: foo
};

var bar = obj.foo; // function reference/alias!

var a = "oops, global"; // `a` also property on global object

bar.call(obj) //2

person.js

var person = {

     firstName: 'John',

     lastName: 'Doe',

     sayHi: function(){
         console.log('Hello '+ this.firstName+'  '+this.lastName); 
    }

}

person.sayHi(); //Hello John Doe

person2.js

function hi(ctx){ 
    ctx.sayHi =function(){
         console.log('Hello '+ this.firstName+'  '+this.lastName); 
    }
}

var person1 = {

     firstName: 'John',

     lastName: 'Doe'
}

var person2= {

     firstName: 'John',

     lastName: 'Roe'
}

hi(person1); 

hi(person2);

person1.sayHi(); //Hello John Doe

person2.sayHi(); //Hello John Roe

person3.js

//[1]
function person (){

     return {
          name: 'John Doe',
          print : function(){
                 console.log(this.name);
          }
     }
}

var obj = person('John Doe'); 
obj.print(); //John Doe

//[2]
function person (name , skill){

     return {
          name: name ,
          print : function(){
                 console.log(this.name);
          },
          skill: {
                name: skill,
                print : function(){
                    console.log(this.name);
                }
          }
     }
}

var obj = person('John Doe', 'Java, AngularJS, NodeJs');
obj.skill.print(); //Java, AngularJS, NodeJs

print.js

//[1]
function print1() {
      console.log( this.name);
}

//[2]
function print2(arg) {
      console.log( this.name + ' '+ arg);
}

//[3]
function print3(arg1, arg2) {
    console.log( this.name + ' ' + arg1 + ' ' + arg2 );
}

var john = {
    
   name: 'John Doe',
   
   skill: 'Java, C'    

}

print1.call(john); //John Doe

print2.call(john , 'age 24'); //John Doe age 24

print3.call(john , 'age 24', 'live in USA'); //John Doe age 24 live in USA

print2.js

//[3]
function print3(arg1, arg2) {
    console.log( this.name + ' ' + arg1 + ' ' + arg2 );
}

var john = {
    
   name: 'John Doe',
   
   skill: 'Java, C'    

}

var data = [ 'age 24', 'live in USA'];

print3.apply(john ,data); //John Doe age 24 live in USA

print3.js

//[3]
function print3(arg1, arg2) {
    console.log( this.name + ' ' + arg1 + ' ' + arg2 );
}

var john = {
    
   name: 'John Doe',
   
   skill: 'Java, C'    

}

var data = [ 'age 24', 'live in USA'];

var fn1 = print3.bind(john ,data);

var fn2 = print3.bind(john ,'age 24', 'live in USA');

fn1();  //John Doe age 24 live in USA

fn2();  //John Doe age 24 live in USA

rectangle.java

public class Rectangle {
    private int x, y;
    private int width, height;
        
    public Rectangle() {
        this(0, 0, 1, 1);
    }
    public Rectangle(int width, int height) {
        this(0, 0, width, height);
    }
    public Rectangle(int x, int y, int width, int height) {
        this.x = x;
        this.y = y;
        this.width = width;
        this.height = height;
    }
}

rectangle2.java

public class Rectangle {
    private int x, y;
    private int width, height;

    public Rectangle(int x, int y, int width, int height) {
        this.x = x;
        this.y = y;
        this.width = width;
        this.height = height;
    }

   public void print_me(){
         System.out.print(this.x +" "+this.y+" "+this.width+" "+this.height);
   }

}

public class App {
    public static void main(String [] args){
          Rectangle rec = new Rectangle (0,0,45,45);
          rec.print_me(); //0 0 45 45
    }
}

rectangle3.js

function Rectangle(x, y , width , height) {
    this.x = x;
    this.y = y;
    this.width = width;
    this.height = height;  
}

Rectangle.prototype = {
    print_me: function(){
         console.log(this.x +" "+this.y+" "+this.width+" "+this.height);
   }
} 

var rec = new Rectangle(0, 0, 45, 45);

rec.print_me(); //0 0 45 45

rectangle4.js

Rectangle.prototype = {
    print_me: function(){
         console.log(this.x +" "+this.y+" "+this.width+" "+this.height);
   },
   calcu: function(num){
       console.log(this.x+this.y+this.width+this.height+num);
  }
} 

var rec = new Rectangle(0, 0, 45, 45);

rec.print_me(); //0 0 45 45

//[1]
rec.calcu.call(rec, 3); //93

//[2]
rec.calcu.apply(rec,[5]); //95

//[3]
var fn = rec.calcu.bind(rec,7);

fn(); //97