the 4 point about This：
1.the use of Object methods
2.the use of constructors
3.the use of ordinary function
4.the use of Function.prototype.call or Function.prototype.apply
<!DOCTYPE html>
<html>
<head lang="en">
<meta charset="UTF-8">
<title>this of point</title>
<script>
/*the use of Object methods*/
var func={
a:2,
getA:function(){
alert(this.a);
}
};
func.getA();
/*the use of ordinary function*/
window.name=‘globle‘;
var getNaem=function(){
return this.name;
};
alert(getName());
/*the use of constructors*/
var myClass=function(){
this.name=‘seven‘;
};
var obj=new myClass();
alert(obj.name);
/*warning：
var myClass=function(){
this.name=‘seven‘;
return{
name:‘jack‘;
}
};
var obj=new myClass();
alert(obj.name);//jack
如果构造器内部显式的返回了一个对象，那么次运算最终返回这个对象；
*/
/*the use of Function.prototype.call or Function.prototype.apply*/
var obj1={
name:‘seven‘,
getName:function(){
return this.name;
}
};
var obj2={
name:‘jezz‘
};
alert(obj1.getName());
alert(obj1.getName.call(obj2));
</script>
</head>
<body>
<div id="div1"></div>
</body>
<script>
/*expanding*/
window.id=‘window‘;
document.getElementById(‘div1‘).onclick=function() {
alert(this.id);//div1
var callback = function () {
alert(this.id);//window
};
callback();
};
/* how to handle about this of point is changed*/
/*Approach 1: keeps this for variables*/
window.id=‘window‘;
document.getElementById(‘div1‘).onclick=function() {
var that=this;
var callback = function () {
alert(that.id);//div1
};
callback();
};
/* Approach 2:ues ‘call‘ change*/*/
window.id=‘window‘;
document.getElementById(‘div1‘).onclick=function() {
var callback = function () {
alert(this.id);//div1
};
callback.call(this);
};
</script>
</html>
时间： 2024-10-05 03:54:02