Javascript中的Call方法讨论

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讨论一下Javascript中 Call的用法

call 方法(版本5.5以上） :

文档中描述：

调用一个对象的一个方法，以另一个对象替换当前对象。

Call([thisObj[,arg1[, arg2[, [,.argN]]]]])

thisObj

可选项。将被用作当前对象的对象。

arg1, arg2, , argN

可选项。将被传递方法参数序列。

测试特性：

[html] view plaincopy

<!DOCTYPE html PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN" "http://www.w3.org/TR/html4/loose.dtd">
<html>
<head>
<meta http-equiv="Content-Type" content="text/html; charset=utf-8">
<title>Test Call</title>
</head>
<body>
<script type="text/javascript">
function Person(name){
this.name = null;
this.showName = function(){
document.write(this.name);
};
this.Init = function(name){
this.name = name;
}
this.Init(name);
};
var jeremy = new Person("Jeremy");
jeremy.showName();
document.write("<br>");
var tom = new Object();
Person.call(tom); //Person class do call()
tom.name = "Tom";
tom.showName();
</script>
</body>

输出：

在这段代码中， NameShowing 类中，showName() 方法，需要有this.name 参数，

所以用call方法，传入实例jeremy.name, 用新对象jeremy替代this指针

[html] view plaincopy

<!DOCTYPE html PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN" "http://www.w3.org/TR/html4/loose.dtd">
<html>
<head>
<meta http-equiv="Content-Type" content="text/html; charset=utf-8">
<title>Test Call</title>
</head>
<body>
<script type="text/javascript">
function NameShowing(){
this.showName = function(){
document.write(this.name);
}
}
function Person(name){
this.name = null;
this.Init = function(name){
this.name = name;
}
this.Init(name);
};
var nameShowing = new NameShowing();
var jeremy = new Person("Jeremy")
//replace the 'this' pointer by jeremy object
nameShowing.showName.call(jeremy);
</script>
</body>
</html>

输出：

jeremy做为一个Person的实例，缺少showName()方法，从NameShowing类中使用call ， jeremy继承了showName（）方法

[html] view plaincopy

<!DOCTYPE html PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN" "http://www.w3.org/TR/html4/loose.dtd">
<html>
<head>
<meta http-equiv="Content-Type" content="text/html; charset=utf-8">
<title>Test Call</title>
</head>
<body>
<script type="text/javascript">
function NameShowing(){
this.showName = function(){
document.write(this.name);
}
}
function Person(name){
this.name = null;
this.Init = function(name){
this.name = name;
}
this.Init(name);
};
var jeremy = new Person("Jeremy")
//pass showName() method to jeremy object
NameShowing.call(jeremy);
jeremy.showName();
</script>
</body>
</html>
<strong>
</strong>

输出：

[html] view plaincopy

<!DOCTYPE html PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN" "http://www.w3.org/TR/html4/loose.dtd">
<html>
<head>
<meta http-equiv="Content-Type" content="text/html; charset=utf-8">
<title>Test Call</title>
</head>
<body>
<script type="text/javascript">
function Person(name, age){
this.name = null;
this.age = null;
this.showPersonInfo = function(){
document.write("Name: " + this.name + "<br>");
document.write("Age: " + this.age + "<br>");
};
this.Init = function(){
this.name = name;
this.age = age;
};
this.Init();
}
var jeremy = new Object();
Person.call(jeremy, "Jeremy", 20);
jeremy.showPersonInfo();
</script>
</body>
</html>