Javascript-创建正则表达式字符类

Question

Is there a way to use javascript's regex engine to create a character class that matches with

" or " (one space before " ) or . or , or [SM_l] or nothing (not the string "nothing" , just 0 characters)

Background Context: This is going to be used as part of the solution to solve the problem presented in this post: Javascript - how to use regex process the following complicated string

Answer 1

You don't a character class. A character class [...] denotes a match on every individual unit of data in it by which ["]+ means characters & , q , u , o , t or ; in any order, with or without all characters:

• "
• &uot;
• ;&

What you need is called grouping. You just need a | inside a grouping construct to imply OR conditions (that I also applied in an answer to your original question )

" or " (one space before " )

means [ ]?"

. or , or [SM_l]

means (\\.|,|\\[SM_l]) that could be reduced to ([.,]|\\[SM_l])

Putting all together you need:

([ ]?"|[.,]|\[SM_l])?

Question mark denotes an optional match.