JS中this/applay/call用法

关于this

this是指调用当前函数的对象。

var test = “tony”
function doSomething(){
	alert(this.test);    // “Tony”
	alert(window.test); // “Tony”
} 

闭包

例子一

var name = “the window”;
var object = {
	name:”My object”,
	doSomething:function(){
		return function(){
			return this.name
		}
	}
}
Alert(object.doSomething()());  // the window

例子二

var name = “the window”;
var object = {
	name:”My object”,
	doSomething:function(){
		var abc = this;
		return function(){
			return abc.name;
		}
	}
}
Alert(object.doSomething()())  // My object;

Call

改变this所指的对象

例子一

var test = “Tony”;
var myobj = {
	test:”TOM”
}
function doSomething(){
	alert(this.test);
}
doSomething.call();   		// “Tony”
doSomething.call(myobj);   // myobj.test 即”TOM”

例子二

function doSomething(name, age){
	alert(this.test + “:” + name +age);
}
doSomething(“Tony”,23);     // Tony:Tony23
doSomething.call(myobj,”Tony”,23);  // Tom:Tony23

Apply

与Call相比它的调用参数的形式不一样。

doSomething.apply(myobj,[“Tony”,23]);