Details of this usage examples in js and details of jsthis instances

Details of this usage examples in js and details of jsthis instances

This example describes how to use this in js. Share it with you for your reference. The details are as follows:

1. Point to window

Global Variables

Alert (this) // Returns [object Window]

Global Functions

function sayHello(){  alert(this);}sayHello();

2. Point to this object (in the global context, this points to window, this points to this object in an object, and this points to window in the closure)

Var user = "the Window"; var box = {user: 'The box', getThis: function () {return this. user;}, getThis2: function () {return this. user ;}}; alert (this. user); // the role walert (box. getThis (); // the boxalert (box. getThis2 (); // the Window (because the closure is used, this points to the window) alert (box. getThis2 (). call (box); // impersonate the box object (here this points to the box object)

3. Use apply and call to change this point of the function.

Function sum (num1, num2) {return num1 + num2;} function box (num1, num2) {return sum. apply (this, [num1, num2]); // this indicates that the window scope box impersonates sum for execution} console. log (box (10, 10); // 20

4. new Object

Function Person () {console. log (this) // point this to a new empty object} var p = new Person ();

I hope this article will help you design javascript programs.