RE

.  :anyone

\d  :any single digital

[^/]+  :1 or >1 until /, / not included

[^abc]+ :1 or >1 until "a" or "b" or "c", "a" or "b" or "c" not included

+  :1 or >1

?  :0 or 1

*  :0 or any

\d{1,3}  :1 or 2 or 3 digital(s)

match :(pattern)

to use content inside() with:\1

class.now_class='201'  ==>  class.now_class='{201}'

ex:             find:(\d{3})   ==>  replace:{\1}

referce : http://www.regular-expressions.info/lookaround.html

look-around:lookahead  &  lookbehind

look-ahead:  ^((?=pattern).)*$  ==>  包含pattern則為true

                      ^(target(?=pattern).)*$  ==>  包含target+pattern則為true

                      ^((?!pattern).)*$  ==>  不包含pattern則為true

                      ^(target(?!pattern).)*$  ==>  不包含target+pattern則為true

look-behind:  ^(.(?<=pattern))*$  ==>  包含pattern則為true

                        ^(.(?<=pattern)target)*$  ==>  包含pattern+target則為true

                        ^(.(?<!pattern))*$  ==>  不包含pattern則為true

                        ^(.(?!pattern)target)*$  ==>  不包含pattern+target則為true

456x56

ex:      find:(?=(\d+)\u\1)  ==>  find 56x56 的開頭起始位置，使用取代會更容易看出效果

比對原則 

在通用式所採用的比對原則是「最大比對（Maximal Match）或是」「貪心比對」（Greedy Match），因此會盡量「貪」到越多的字元越好。

若使用通用式 'foo.*bar' 來比對字串 'The food is under the bar in the barn.'，所比對到的是長字串 ‘food is under the bar in the bar’，而不是另一個符合比對標準的短字串 ‘food is under the bar’。

若要使通用式進行極小比對（Minimal Match），也就是在符合比對的條件下，選擇最短的字串，那麼就要在星號之後加上問號。