The purpose of the apply (or call) method in JavaScript----inheritance of objects

All along, my understanding is that the function.apply (or Function.call) method in JS is to change the function's execution context (Excute context), in other word, to change the scope of the function at execution time,

The most immediate is the value that affects this predefined variable.!! Function.apply (obj, arguments) is the change function execution environment for the incoming obj object, that is, Funtion internal this will be changed to obj.

The following example is a search for someone else's example.

Let's look at an example.

function Person (name,age,grade) {   //define a class, human      this.name=name;     Name      this.age=age;       Age     this.sayhello=function () {alert (grade)}, function Student (name,age,grade,school) {    //Student class     Person.apply (this,arguments); for (var i in arguments) {alert (arguments[i])}        This.grade=grade;                Grade     This.school=school;                 School} stu = new Student (' Yuanshao ', +, ' university ', ' Huaqiao ') Stu.sayhello ();//So Stu has the SayHello () method in the person constructor.

Explain:

The Apply method can hijack another object's method, inheriting another object's properties

Function.apply (Obj,args) method can receive two parameters

obj: This object will replace the This object in the function class

Args: This is an array, which is passed as a parameter to function (args-->arguments)

Let's look at an example:

Alert (Math.max (5,8,9,11))   //8 can ———————————— var arr=[5,7,9,1]alert (Math.max (arr))    //This is not possible. —————————————————————— var Arr=[5,7,9,1]alert (Math.max.apply (Null,arr))    //This is OK. It must be written like this.

　　

The purpose of the apply (or call) method in JavaScript----inheritance of objects