str为要去除空格的字符串:
去除所有空格:
str = str.replace(/\s+/g,"");
去除两头空格:
str = str.replace(/^\s+|\s+$/g,"");
去除左空格：
str=str.replace( /^\s/, '');
去除右空格：
str=str.replace(/(\s$)/g, "");

SCRIPT LANGUAGE="JavaScript">

</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>

去除所有空格:
str = str.replace(/\s+/g,"");
去除两头空格:
str = str.replace(/^\s+|\s+$/g,"");
去除空格(TimeSheet用过)
arg0=arg0.replace(/\s+$|^\s+/g,"");