JavaScript regular expression check number only

Question

I want a regular expression for the following values:

1) .1 = False.
2) 0.1 = True.
3) 1.1245 = True.
4) 1.2. = False.
5) 1.24.35 = False.
6) 21.152 = true.

This regex should check that the string represents an integer or is composed of only numbers and a single . representing a decimal point.

I am using: /^[\+\-]?\d*\.?\d+(?:[Ee][\+\-]?\d+)?$/ but it takes "1.2." as true.

You should post what regex you have tried that did not work. — takendarkk
– takendarkk, Commented Nov 17, 2017 at 21:10
/^[\+\-]?\d*\.?\d+(?:[Ee][\+\-]?\d+)?$/.test('1.2.') returns false, not true. Cannot reproduce what you are saying. — trincot
– trincot, Commented Nov 17, 2017 at 21:14
@trincot when I enter 1.2. in text box and print in console.log it shows true, but when I use 1.2.1 then it showing false. I want 1.2. should show false. — Vinit Mehta
– Vinit Mehta, Commented Nov 17, 2017 at 21:19
If you are open to other solutions and not restricted to just a regular expression, I'd suggest Number(x) === Number(x); when NaN, it will return false because NaN === NaN always returns false. — rishat
– rishat, Commented Nov 17, 2017 at 21:26
@RishatMuhametshin could you please demonstrate with any example. — Vinit Mehta
– Vinit Mehta, Commented Nov 17, 2017 at 21:28

U Rogel · Accepted Answer · 2017-11-17 21:41:10Z

2

You are taking the first digits set as none or more \d*, you should use \d+, then it would work for the cases you want.

Can also look here

Edit: ^[\+\-]?\d+(\.?\d+(?:[Ee][\+\-]?\d+)?)?$

edited Nov 17, 2017 at 21:41

answered Nov 17, 2017 at 21:26

U Rogel

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11 Comments

Vinit Mehta Over a year ago

when I enter single digit then it display false.

Vinit Mehta Over a year ago

Its unstable it is not working for other like "012.5.".

U Rogel Over a year ago

"012.5." should return false or?

Vinit Mehta Over a year ago

Yes it is working fine in regex101.com/r/yXw3yB/1 but when I am using like below it return true for "1.2.". var reg = /^[\+\-]?\d+(\.?\d+(?:[Ee][\+\-]?\d+)?)?$/ console.log(reg.test((edValue.value)));

Vinit Mehta Over a year ago

I want only one dot enter in the string. if you put second dot it should be false.

|

maniak1982 · Accepted Answer · 2017-11-17 22:09:19Z

0

If you use the following regex

(?:\d*.)?\d+

It will match only real numbers.

If the input is like 1.2.3 it will return 1.2.

Hope it helps!

edited Nov 17, 2017 at 22:09

maniak1982

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answered Nov 17, 2017 at 21:42

Tulrose Deori

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Comments

dark.semiQ · Accepted Answer · 2017-11-17 22:27:52Z

0

you were puting the dot in the wrong place this should work

[\+\-]?[0-9]+(\.[0-9]+(?:[Ee][\+\-]?[0-9]+)?)?

edited Nov 17, 2017 at 22:27

answered Nov 17, 2017 at 22:11

dark.semiQ

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Comments

rusmus · Accepted Answer · 2017-11-18 08:38:52Z

0

Your regex seems more complex than it needs to be. In order to live up to your requirements (starts with a number, ends with a number, at most one dot) you can use the following:

(^\d+\.\d+$)|(^\d+$)

Edit: Or even simpler:

^\d+(\.\d+)?$

edited Nov 18, 2017 at 8:38

answered Nov 17, 2017 at 21:29

rusmus

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2 Comments

Vinit Mehta Over a year ago

When I use "12.2." it returns true, if I changes with "12.2.3" then its working file. I want it should show false when I use "12.2.".

rusmus Over a year ago

I can't reproduce that behavior. Are you sure that the error isn't in the surrounding code?

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