???? <script language="javascript">
???????????? var strM = "javascript is a good script language";
??????????? ?//在此将字母a全部替换成字母A
???????????? alert(strM.replace(/a/g,"A"));

?????????? //下面是不分大小写都替换

?????????? alert(s.replace(/a|A/g,"B"));
????? </script>

?

?

来源：

http://blog.163.com/wengqichy@yeah/blog/static/94464926200892781530138/