JavaScript中this的一些怪異現象

標籤：

 <!--JavaScript偽協議和內聯事件對於this的指向不同-->    <a href="#" onclick="alert(this.tagName);">click me</a><!--彈出A-->    <a href="javascript:alert(this.tagName);">click me</a><!--彈出undefined-->    <a href="javascript:alert(this==window);">click me</a><!--彈出true-->    <input id="btn" type="button" value="this demo" name="button"/>

 

<script type="text/javascript">               var name = ‘somebody‘;        var angela = {            name: ‘angela‘,            say: function () {                alert("I‘m " + this.name);            }        };        var btn = document.getElementById(‘btn‘);        //setTimeout和setInterval也會改變this的指向        /*        angela.say();//I‘m  angela        setTimeout(angela.say, 1000);//I‘m  somebody        setInterval(angela.say, 1000);//I‘m  somebody        */        //on...也會改變this的指向        /*                angela.say();//I‘m  angela        btn.onclick = angela.say;//I‘m  button        */        //匿名函數調整this指向        setTimeout(function () { angela.say(); }, 1000);//I‘m  angela        setInterval(function () { angela.say(); }, 1000)//I‘m  angela        btn.onclick = function () { angela.say(); };//I‘m  angela        setTimeout(function () { alert(this == window); }, 1000);//true        btn.onclick = function () { alert(this == btn); }//true        //call 和 apply調整this的指向        angela.say.call(btn);//I‘m  button        setTimeout(function () { angela.say.call(btn); }, 1000);//I‘m  button        setTimeout(function () { angela.say.apply(btn); }, 1000);//I‘m  button        btn.onclick = function () { angela.say.apply(btn); }//I‘m  button        //將this指向的對象儲存到變數        var name = ‘migo‘;        var mydemo = {            name: ‘angela‘,            say: function () {                alert("I‘m " + this.name);            },            init: function () {                var that = this;                document.getElementById(‘btn‘).onclick = function () {                    that.say();//I‘m angela                    this.say();//這兒報錯 this.say is not function                }            }        };    </script>

JavaScript中this的一些怪異現象