请问这个正则表达式该怎么写?

Question

<SCRIPT LANGUAGE="JavaScript">
<!--
var s1 = ",7,3,4,5,6,1,2,"
var the = /(,1(?=,))|(,2(?=,))/gi
alert( s1.replace( the , "" ) )
//-->
</SCRIPT>

Answer 1

<SCRIPT LANGUAGE="JavaScript">
<!--
var s1 = ",7,3,4,5,6,1,2,"
var the = /,[12](?=,)/gi
alert( s1.replace( the , "" ) )
//-->
</SCRIPT>

Answer 2

<SCRIPT LANGUAGE="JavaScript">
<!--
var s1 = ",7,3,4,5,6,1,2,"
var the = /,1(?=,)|,2,/gi
alert( s1.replace( the , "," ) )
//-->
</SCRIPT>

Answer 3

多谢楼上.可能是我举例不当,实际遇到的情况可能是:
var s1 = ",77,33,44,55,66,11,22,"
var the = /(,11(?=,))|(,22(?=,))/gi
alert( s1.replace( the , "" ) )另外,小弟真正想解决的问题是这样的:假如我想把"11,22"保留下来,而去除掉",77,33,44,55,66,",请问怎么办?另外,可否讲解一下,或给一些资料,小弟想知道原理.小弟必另有重谢!
谢谢!

Answer 4

<SCRIPT LANGUAGE="JavaScript">
<!--
var s1 = ",77,33,44,55,66,11,22,"
var the = /,(?!11,|22,)[^,]+/gi
alert( s1.replace( the , "" ) )
//-->
</SCRIPT>
你可以查下预查资料