 
//供使用者調(diào)用 
function trim(s){ 
return trimRight(trimLeft(s)); 
} 
//去掉左邊的空白 
function trimLeft(s){ 
if(s == null) { 
return ""; 
} 
var whitespace = new String(" \t\n\r"); 
var str = new String(s); 
if (whitespace.indexOf(str.charAt(0)) != -1) { 
var j=0, i = str.length; 
while (j < i && whitespace.indexOf(str.charAt(j)) != -1){ 
j++; 
} 
str = str.substring(j, i); 
} 
return str; 
} 
//去掉右邊的空白 
function trimRight(s){ 
if(s == null) return ""; 
var whitespace = new String(" \t\n\r"); 
var str = new String(s); 
if (whitespace.indexOf(str.charAt(str.length-1)) != -1){ 
var i = str.length - 1; 
while (i >= 0 && whitespace.indexOf(str.charAt(i)) != -1){ 
i--; 
} 
str = str.substring(0, i+1); 
} 
return str; 
} 

使用時(shí)只需調(diào)用trim函數(shù)即可。
下面是用正則的實(shí)現(xiàn)方法：

復(fù)制代碼代碼如下:

 
<SCRIPT LANGUAGE="JavaScript"> 
<!-- 
String.prototype.Trim = function() 
{ 
return this.replace(/(^\s*)|(\s*$)/g, ""); 
} 
String.prototype.LTrim = function() 
{ 
return this.replace(/(^\s*)/g, ""); 
} 
String.prototype.RTrim = function() 
{ 
return this.replace(/(\s*$)/g, ""); 
} 
//--> 
</SCRIPT> 
<input type="text" value="    前后都是空格   " id="space"> 
<input type="button" value="去前后空格" onclick="javascript:document.getElementById('space').value=document.getElementById('space').value.Trim();document.getElementById('space').select();"> 
<input type="button" value="去前空格" onclick="javascript:document.getElementById('space').value=document.getElementById('space').value.LTrim();document.getElementById('space').select();"> 
<input type="button" value="去后空格" onclick="javascript:document.getElementById('space').value=document.getElementById('space').value.RTrim();document.getElementById('space').select();"> 
<input type="button" value="還原" onclick="javascript:document.getElementById('space').value='    前后都是空格     ';"> 