JavaScript中this的9种应用场景及三种复合应用场景

this.a = 10;alert(a);//10b = 20;alert(this.b);//20var c = 30;alert(this.c);//30

var a = 10;var bar = { a: 20, test: function(){  alert(this.a); }}bar.test();//20

var a = 10;function foo(){ alert(this.a);}foo();//10

var a = 10;var foo = { a: 20, fn: (function(){  alert(this.a); })()}foo.fn//10

var a = 10;var oTimer1 = setInterval(function(){ var a = 20; alert(this.a);//10 clearInterval(oTimer1);},100);

(function(){ eval("alert(this)");//[object Window]})();function Foo(){ this.bar = function(){  eval("alert(this)");//[object Object] }}var foo = new Foo();foo.bar();

function Person(name,age){ this.name = name; this.age = age; this.sayName = function(){  alert(this.name); }}var p1 = new Person('lily','20');p1.sayName();//'lily'

(function(){ var f = new Function("alert(this)"); f();//[object Window]})();function Foo(){ this.bar = function(){  var f = new Function("alert(this)");  f();//[object Window] }}var foo = new Foo();foo.bar();

var a = 10;var foo = { a: 20, fn: function(){  alert(this.a); }};var bar ={ a: 30}foo.fn.apply();//10(若参数为空，默认指向全局对象)foo.fn.apply(foo);//20foo.fn.apply(bar);//30

var someone = { name: "Bob", showName: function(){  alert(this.name); }};var other = { name: "Tom", showName: someone.showName}other.showName();　　//Tom//以上函数相当于var other = { name: "Tom", showName: function(){  alert(this.name); }}other.showName();　　//Tom

var name = 2;var a = { name: 3, fn: (function(){  alert(this.name); })(), fn1:function(){  alert(this.name); }}a.fn;//2[匿名函数中的this指向全局对象]a.fn1();//3[对象内部函数的this指向调用函数的当前对象]

var name = "Bob"; var nameObj ={  name : "Tom",  showName : function(){  alert(this.name); },  waitShowName : function(){  var that = this;  setTimeout(function(){   that.showName();  }, 1000); }}; nameObj.waitShowName();//"Tom"[that=this改变this的指向，使this从指向全局变量变化到指向nameObj]var name = "Bob"; var nameObj ={  name : "Tom",  showName : function(){   alert(this.name);  },  waitShowName : function(){  var that = this;//that指向nameObj  setTimeout(function(){   (function(){     alert(this.name);   })();  }, 1000); }}; nameObj.waitShowName();// 'Bob'[形成匿名函数，this指向全局变量]