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This article will explain in detail how to use Call and apply. The editor thinks it is very practical, so I share it with you as a reference. I hope you can get something after reading this article.

. Each function contains two non-inherited functions: call,apply. Calling a function in a specific scope is actually equivalent to the value of the this object in the function body

Call, one of the uses of apply is to pass parameters. What's actually powerful is that it expands the scope of the function.

Eg1: (pass parameters)

/ / ~ ~

Function sum (XBI y) {

Return Xeroy

}

Function call1 (N1 and N2) {

Return sum. Call (this,n1,n2); / / ~ return sum.apply (this, [N1 ~ N2])

}

Alert (call1 (100.20)); / / alert (30)

/ / ~ ~

Eg2: (scope extension) benefit: objects and methods are not coupled

/ / ~ ~

Window.color = 'red'

Var obj = {color: 'blue'}

Function showColor () {

Alert (this.color)

}

ShowColor.call (window); / / showColor.call (this); / / red

ShowColor.call (obj); / / blue

/ / ~ ~

/ / ~ ~

/ / Custom object

Function Obj (x, y) {

This.x = x

This.y = y

Return Xeroy

}

/ / method

Function fun (a, b) {

Return a + b

}

Var obj = new Obj (10,20)

Alert (fun. Call (obj, obj.x, obj.y); / / 30

/ / ~ ~

Let me give you a few specific examples:

Example 1:

Function add (afort b)

{

Alert (aquib)

}

Function sub (afort b)

{

Alert (aMub)

}

/ / add.call (sub,3,1)

Add.apply (sub, [3jue 1])

Example 2:

Function Class1 ()

{

This.name = "class1"

This.showNam = function ()

{

Alert (this.name)

}

}

Function Class2 ()

{

This.name = "class2"

}

Var C1 = new Class1 ()

Var c2 = new Class2 ()

/ / c1.showNam.call (c2); / / class2

C1.showNam.apply (c2)

Example 3:

Var func=new function () {this.a= "func"}

/ / var func = {a: "func"}

Var myfunc=function (x) {

Var a = "myfunc"

Alert (this.a)

Alert (x)

}

/ / myfunc.apply (func, "var")

Myfunc.apply (func, ["var"])

Example 4: [is there any call that can be used to implement inheritance]

Function Class1 ()

{

This.showTxt = function (txt)

{

Alert (txt)

}

}

Function Class2 ()

{

Class1.call (this)

}

Var c2 = new Class2 ()

C2.showTxt ("cc")

Example 5: multiple inheritance [how javaScript simulates object-oriented inheritance and can also implement multiple inheritance]

Function Class10 ()

{

This.showSub = function (afort b)

{

Alert (aMub)

}

}

Function Class11 ()

{

This.showAdd = function (afort b)

{

Alert (aquib)

}

}

Function Class2 ()

{

Class10.call (this)

Class11.call (this)

}

Var c2 = new Class2 ()

C2.showAdd (1B4); / / 5

C2.showSub (10jue 6); / / 4

This is the end of the article on "how to use Call and apply". I hope the above content can be of some help to you, so that you can learn more knowledge. if you think the article is good, please share it for more people to see.

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