通过正则表达式可以实现题目要求具体代码如下：
<html>
<head>
<script language="javascript">
String.prototype.trim = function(){
return this.replace(/^\s+|\s+$/g,"")
}
var testStr = " this is a dog ";
alert("&&&&"+testStr.trim()+"&&&&");
</script>
</head>
<body>
<div id="id1"><a href="#" onclick="aone('id1')">innerText</a></div>
<div id="id2"><a href="#" onclick="aone('id2')">innerHTML</a></div>
<div id="test">
<span style="color:red">test1</span> test2
</div>
<a href="javascript:alert(test.innerHTML)">innerHTML</a>
<a href="javascript:alert(test.innerText)">innerText</a>
<a href="javascript:alert(test.outerHTML)">outerHTML</a>
</body>
</html>
?