一、指向window,即全局对象
1 this
2 //Window {speechSynthesis: SpeechSynthesis, caches: CacheStorage, localStorage: Storage, sessionStorage: Storage, webkitStorageInfo: DeprecatedStorageInfo…}
1 var a =12;
2
3 function (){
4 console.log(this.a);
5 }
6
7 function aaa(){
8 console.log(this.a);
9 }
10
11 aaa();
12 12
二、指向构造函数的实例化对象
1 function Page(url,name){
2 this.url=url;3 this.name = name;6 }
7
8 var page1 = new Page("https://i.cnblogs.com","blogs");
page1.url;
// "https://i.cnblogs.com/"
三、使用Apply或call,指向调用它的第一个参数
1 function foo() {
2 console.log( this.a );
3 }
4 var obj = {
5 a:2
6 };
7 foo.call( obj );
8 // 2
四、指向调用方法的对象
1 function test(){
2 console.log(this.x);
3 }
4 var o = {
5 x : 3
6 };
7 o.m = test;
8 o.m();
9 // 3
