去除字符串最后一个字符

[loveshuang942]

比如 "abc,def,asd," 我想把最后一个逗号去掉 该怎么做？

[Click_Me]

<SCRIPT LANGUAGE="JavaScript">
<!--
var str = "abc,def,asd,";
	alert(str.substring(0,str.length-1))
//-->
</SCRIPT>