CODEWITHSUNDEEP
regex
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Reputation: 83

Regex - numeric only with negatives allowed, but only one leading zero

I'm struggling to find a way to allow numeric only numbers that can also be negative, but also allow only one leading zero.
Goal Examples: 0, 12345, -555 Bad Examples: -0, 01235, -012

I have the following so far, but cant seem to work in the negative character properly. If I type - first nothing can be typed afterwards, but it should allow 1-9: /^([-0]|[1-9]\d*)$/

Tried this as well, but no luck: /^[-]?(0|[1-9]\d*)$/

Any help would be greatly appreciated.

----updated code---- //can type in a 0, but not a hypen for negative. If I rotate the ?:0|-? to be ?:-|0? I can then type in the hypen, but not a zero.

function(evt) {

            evt = (evt) ? evt : window.event;
            let expect = evt.target.value.toString().trim() + evt.key.toString();
           
            if (!/^(?:0|-?[1-9][0-9]*)$/.test(expect)) {
                evt.preventDefault();
            } else {
                return true;
            }

Upvotes: 0

Views: 58

Answers (2)

John Williams
John Williams

Reputation: 5375

Try the following: (see here)

\b0\b|-?\b(?!^0)[1-9]+[0-9]*\b

Upvotes: 1

Tim Pietzcker
Tim Pietzcker

Reputation: 336158

Let's keep it simple:

/^(?:0|-?[1-9][0-9]*)$/

Explanation:

^       # Start of string
(?:     # Start of non-capturing group
 0      # Match either a zero (and nothing else)
|       # or
 -?     # an optional -
 [1-9]  # a digit between 1 and 9
 [0-9]* # 0 or more further digits
)       # End of group
$       # End of string

Upvotes: 1

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