Regex to match digits only if not followed or proceeded by letters in Javascript

Question

I would like to match digits but not when they are within words (in JavaScript).

The following should match:

1
1,2
1.5-4 (matches 1.5 & 4 separately)
(1+3) (matches 1 & 3 separately)
=1;

The following should NOT match:

FF3D
3deg

I thought I could solve with with a negative lookahead, like so: (?![A-Za-z]+)([0-9]+[\\.|\\,]?[0-9]?) but it does not work.

How can I best solve this? Thanks.

Answer 1

I would like to match digits but not when they are within words.

You can use look arounds in your regex:

\b\d*[,.]?\d+\b

• \\b is for word boundary

RegEx Demo

Answer 2

2021 update:

Since lookbehind support has grown considerably, it makes sense to use a lookbehind based solution:

/(?<![a-z])\d*[.,]?\d+(?![a-z])/gi         # ASCII only
/(?<!\p{L})\p{N}*[.,]?\p{N}+(?!\p{L})/giu  # Unicode-aware

See the regex demo . Please track the lookbehind and Unicode property class support here .

Details

• (?<![az]) - no ASCII letter (or any Unicode letter if \\p{L} is used) allowed immediately to the left of the current location
• \\d*[.,]?\\d+
• (?![az]) - no ASCII letter (or any Unicode letter if \\p{L} is used) allowed immediately to the right of the current location.

Original answer

In order to match any standalone integer or float numbers with dot or comma as decimal separator you need

/(?:\b\d+[,.]|\B[.,])?\d+\b/g

See the regex demo . The point here is that you cannot use a word boundary \\b before a . since it will invalidate all matches like .55 (only 55 will be matched).

Details :

• (?:\\b\\d+[,.]|\\B[.,])? - either of the two alternatives:
  • \\b\\d+[,.] - a word boundary (there must be a non-word char before or start of string), then 1+ digits, and then a . or ,
  • | - or
  • \\B[.,] - a position other than word boundary (only a non-word char or start of string) and then a . or ,
• \\d+ - 1+ digits
• \\b - a word boundary.

 const regex = /(?:\\b\\d+[,.]|\\B[.,])?\\d+\\b/g; const str = `.455 and ,445 44,5345 435.54 4444 1 1,2 1.5-4 (1+3) =1; FF3D 3deg`; console.log(str.match(regex));

If you need to also add support for the exponent use:

/(?:\b\d+[,.]|\B[.,])?\d+(?:e[-+]?\d+)?\b/ig

Answer 3

Try This

var pattern= /([\d.]+)/;

https://regex101.com/r/q1qDHV/1