SCRIPT LANGUAGE="JavaScript">   
<!--   
//出处:网上搜集   
// Trim() , Ltrim() , RTrim()   
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="还原" onclick="javascript:document.getElementById('space').value='     前后都是空格    ';">

<a href="http://www.yaoasnsi.com" target="_blank">访问yaosansi.com</a>