jquery lesson Fourth The use of this in JavaScript

thisUse of keywords

Using in JavaScriptthisThe keyword represents the object that invokes the method, which is the same as most object-oriented languages. But becausecall、apply、bindThe effects of such functions, we can changethisThe object being referred to.

• using call or apply function called, this refers to the first parameter passed in the object, if the incoming null or undefined , which represents the global object (window ).
• Calls a function (method) through an object that represents the object in the function that this called the function.
• Represents a global object in a function that is called alone this .

var MyObject = {    SayHello: function() {        Console.Log("Hi, my name is" +  This.MyName);    },    MyName: "Rebecca"};var Secondobject = {    MyName: "Colin"};MyObject.SayHello();    //"Hi, my name is Rebecca"MyObject.SayHello.Pager(Secondobject);   //"Hi, my name is Colin"

var MyName = "The Global object";var SayHello = function() {    Console.Log("Hi, my name is" +  This.MyName);};var MyObject = {    MyName = "Rebecca"};var Myobjecthello = SayHello.Bind(MyObject);SayHello(); //"Hi, my name is the global object"Myobjecthello(); //"Hi, my name is Rebecca"

JavaScript can dynamically add functions to objects in the run, which will also result in this changes to the surrogate object.

var MyName = "The Global object";var SayHello = function() {    Console.Log("Hi, my name is" +  This.MyName);};var MyObject = {    MyName: "Rebecca"};var Secondobject = {    MyName: "Colin"};MyObject.SayHello = SayHello;Secondobject.SayHello = SayHello;SayHello(); //"Hi, my name is the global object"MyObject.SayHello(); //"Hi, my name is Rebecca"Secondobject.SayHello(); //"Hi, my name is Colin"

Also, you cannot directly add a short reference to a function that is in a darker namespace, causing this it to become a global object, but you can set a short reference to the object it is located in.

var MyNamespace = {    MyObject: {        SayHello: function() {            Console.Log("Hi, my name is" +  This.name);        },        MyName: "Rebecca"    }};var Hello = MyNamespace.MyObject.SayHello;Hello();    //"Hi, my name is undefined"var obj = MyNamespace.MyObject;obj.SayHello(); //"Hi, my name is Rebecca"

Tips

< Code style= "font-family: ' Ubuntu mono ', Consolas, ' Liberation Mono ', courier,monospace; Font-size:1em; padding:2px 5px ">call with apply is that apply receives two parameters: this and an array of arguments to the function, while call is this , but is followed by the argument list of the function.

This document is organized by the Changsha Camp David Education .

jquery lesson Fourth The use of this in JavaScript