Javascript: Regular expression to allow negative and positive floating point numbers?

Question

I'm trying to write a regular expression to match both positive and negative floating points of any length of characters. I tried this

/^-|[0-9\ ]+$/

However this is still wrong because for example it would match "46.0" and "-46.0" but will also match "4-6.0" which I don't want.

At the moment i'm using this

/^-|[0-9][0-9\ ]+$/

This fixes the first problem but this will match something like "-4g" and that is also incorrect.

What expression can I use to match negative and positive floating points?

possible duplicate of [How to detect a floating point number using a regular expression](http://stackoverflow.com/questions/2293780/how-to-detect-a-floating-point-number-using-a-regular-expression) — Dave Newton, Nov 06 '11 at 03:40
This comes up first searching for "regex for negative float" — user2105469, Mar 12 '14 at 18:36

score 7 · Answer 1 · answered Nov 06 '11 at 03:31

7

Why not the following?

parseFloat(x) === x

If you really want a regex, there are entire pages on the internet dedicated to this task. Their conclusion:

/^[-+]?[0-9]*\.?[0-9]+$/

or

/^[-+]?[0-9]*\.?[0-9]+([eE][-+]?[0-9]+)?$/

if you want to allow exponential notation.

answered Nov 06 '11 at 03:31

Domenic

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1

doesn't allow for "42." which is a perfectly valid JS number. also, 42.e3 isn't matched like it should be. – Kyle Simpson Aug 12 '13 at 14:59

score -1 · Answer 2 · answered Jul 30 '15 at 13:30

-1

Well mine is bit lesser, optional you can remove {1,3} limits to minimum 1 and max 3 numbers part and replace that with + to make no limit on numbers.

/^[\-]?\d{1,3}\.\d$/

answered Jul 30 '15 at 13:30

STEEL

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score -1 · Answer 3 · answered Jun 08 '17 at 11:06

-1

Try this...

I am sure, it's work in javascript.

var pattern = new RegExp("^-?[0-9.]*$");

if (pattern.test(valueToValidate)) {

   return true;

} else {

 return false;

}

answered Jun 08 '17 at 11:06

user3414092

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5

Thank you for this code snippet, which may provide some immediate help. A proper explanation [would greatly improve](//meta.stackexchange.com/q/114762) its educational value by showing *why* this is a good solution to the problem, and would make it more useful to future readers with similar, but not identical, questions. Please [edit] your answer to add explanation, and give an indication of what limitations and assumptions apply. In particular, does it accept `3.4.5`? (It shouldn't) How about the empty string? – Toby Speight Jun 08 '17 at 11:30

score -1 · Answer 4 · answered Nov 06 '11 at 03:34

-1

/^[-+]?[0-9]+(?:\.[0-9]+)?(?:[eE][-+][0-9]+)?$/

This also allows for an exponent part. If you don't want that, just use

/^[-+]?[0-9]+(?:\.[0-9]+)?$/

Hope this helps.

answered Nov 06 '11 at 03:34

Niet the Dark Absol

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Javascript: Regular expression to allow negative and positive floating point numbers?

4 Answers4

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