r=reg
for i=1 to len(reg)
if right(left(reg,i),1)="a" and right(left(reg,i-1),1)<>"a" and right(left(reg,i+1),1)<>"a" then
r=left(r,i-1)&"aa"&left(r,i+1)
end if
next
for i=1 to len(reg)
if right(left(reg,i),1)="a" and right(left(reg,i-1),1)<>"a" and right(left(reg,i+1),1)<>"a" then
r=left(r,i-1)&"aa"&left(r,i+1)
end if
next
var reg = /([^a])a([^a])/g;//我需要的正则式
return str.replace(reg,'$1aa$2');
}
"ronakitty(毓苫) ",兄弟,你用的不是正则式
替换后
123aa456
不使用$1aa$2
替换后
12aa56
([^a])a([^a]) ([^a])//$1......a........([^a])//$2
不知到您懂了吗?
浅的教程:
http://www.pconline.com.cn/pcedu/empolder/wz/php/0501/533294.html
深入的话,去看一下perl的书