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How to use the call method of javascript
- 青灯夜游Original
- 2021-04-12 14:59:499700browse
In JavaScript, the call method can be used to call a method instead of an object. It can change the object context of a function from initialization to a new object, that is, the original object in the brackets is changed to call() the previous object.
The operating environment of this tutorial: windows7 system, javascript version 1.8.5, Dell G3 computer.
Usage of call() method in js
1.call method
Syntax: call(thisobj,[argq,arg2])
Definition: Call a method of an object and replace the current object with another object
Description:
The call method can be used to call a method instead of an object. The call method can change the object context of a function from initialization to a new object, that is, the original object in the brackets is changed to the object before call(), which is ready to use. thisobj replaces the thing before call, and finally uses thisobj object to execute the method before call.
If the thisObj parameter is not provided, the Global object is used as thisObj.
Just like
<!DOCTYPE html>
<html>
<head>
<meta charset="UTF-8">
<title>js中call方法的使用</title>
</head>
<body>
<p id="id1">新年</p>
</body>
</html>
<script>
function add(a,b){
alert(a+b);
}
function sub(a,b){
alert(a-b);
}
document.getElementById("id1").onclick = function(){
add.call(sub,3,1);
}
</script>add replaces sub , the most summarized output is
The meaning in this example is to use add to replace sub, add.call(sub,3,1) == add(3,1), so the running result is: alert(4); // Note: functions in js are actually objects, and the function name is a reference to the Function object.
[Recommended learning: javascript advanced tutorial]
2.apply method
Syntax: apply(thisobj ,[argArray])
Definition: Apply a method of a certain object and replace the current object with another object
Description:
If argArray is not a A valid array or not an arguments object, a TypeError will result.
If neither argArray nor thisObj is provided, the Global object will be used as thisObj and no parameters can be passed.
<!DOCTYPE html>
<html>
<head>
<meta charset="UTF-8">
<title>js中call方法的使用</title>
</head>
<body>
<p id="id1">新年</p>
</body>
</html>
<script>
function Animal(){
this.name = "Animal";
this.showName=function(){
alert(this.name);
}
}
function Cat(){
this.name = "Cat";
}
document.getElementById("id1").onclick = function(){
var animal = new Animal();
var cat = new Cat();
// 通过call或apply方法，将原本属于Animal对象的showName方法交给对象call来使用了
animal.showName.apply(cat,[]);
animal.showName.call(cat,",");
}
</script>Note that the parameters of apply are different from those of the call method. apply is an array
3.call implements js inheritance
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