Firebase rules regex troubles

Question

^([-+]?)([\d]{1,2})(((\.)(\d+)(,)))(([-+]?)([\d]{1,3})((\.)(\d+))?)$

I am trying to use this regex above to be able to confirm that the data is a valid coordinate. I am having trouble getting this to work with Firebase rules. When i run the regex in an online regex tester, it works okay, but Firebase rules doesn't seem to accept it.

Here is my firebase rule:

".validate": "newData.isString() && newData.val().matches(/^([-+]?)([\d]{1,2})(((\.)(\d+)(,)))(([-+]?)([\d]{1,3})((\.)(\d+))?)$/)"

Is there anyway to get this working?

Answer 1

You need to double the escaping backslashes, but honestly, your expression contains too many redundant grouping constructs.

Use

.matches(/^[-+]?\\d{1,2}\\.\\d+,[-+]?\\d{1,3}(\\.\\d+)?$/)

or avoid the backslashes altogether:

.matches(/^[-+]?[0-9]{1,2}[.][0-9]+,[-+]?[0-9]{1,3}([.][0-9]+)?$/)

The regex will match strings like in this online demo.

Details:

• ^ - start of string (in Firebase regex, it is an anchor when used at the start of the pattern only)
• [-+]? - 1 or 0 + or -
• [0-9]{1,2} - 1 or 2 digits
• [.] - a dot
• [0-9]+ - 1+ digits
• , - a comma
• [-+]? - 1 or 0 + or -
• [0-9]{1,3} - 1 to 3 digits
• ([.][0-9]+)? - 1 or 0 sequences of . and 1+ digits (note that non-capturing groups are not supported)
• $ - end of string anchor (only when at the pattern end, $ matches the end of string in Firebase regex).