正则表达式只匹配一组字符中的一个字符

Question

I have a following regular expression that works fine(with one exception that works fine, that I already know how to fix). I would like to allow a user to prepend the input with > or <, but with a limit of 1.

I don't know how to allow one character of a set of characters.

Here is the expression

var valid = new RegExp('^-?['+rangeMin+'-'+rangeMax+']$');

Update: So there are two characters(>,<) a user can prepend(prefix) a value, he can enter > or <. So if a user enters > he cant't enter > or < anymore and if he enters < he cant't enter > or <. Sorry guys, tried googling it but, that was a little to advance ;/

Answer 1

You may use

var valid = new RegExp('^[<>]?-?['+rangeMin+'-'+rangeMax+']$');

The [<>]? is a character class that matches a single character, either > or < , 1 or 0 times due to ? quantifier.