Regular Expression for negative and positive decimal numbers

Question

I'm trying to create a regular expression using javascript for react application that allow negative and positive decimal numbers and not allow enter any character.

I've been looking for examples, reading documentation but I dont know how make it.

This are the things that have to do:

allow negative and positive decimal numbers, I found this:

var re = new RegExp("^[+-]?[0-9]{0,900}(?:\.[0-9]{0,900})?$");

but I can write a character and show me true and add other character and show me false. console.log(re.test(value));

if is decimal and starts with zero show zero (0.232) and dont allow this (.232)

dont allow write characters, I've seen this /^\d*$/

looks like duplicate from the following [quetion](https://stackoverflow.com/questions/16460773/regex-validate-negative-and-positive-decimal-numbers/16461060) — Dekel Zoaretz, May 03 '18 at 08:01
For "allow negative and positive decimal numbers and not allow enter any character" try this : ^-?[0-9]\d*(\.\d+)?$ — Chintan, May 03 '18 at 08:03
no, I dont want a limit of digits... and I'm using an input type text and I dont want allow characters and not use a type number — Javier, May 03 '18 at 08:04
@JaviLesPaul you just wanna make sure your input type `text` only gets numbed in it right ? — Muhammad Usman, May 03 '18 at 08:05

The fourth bird · Accepted Answer · 2018-05-03T09:04:16.453

Looking at the documentation about RegExp it states that when using the constructor function, the normal string escape rules (preceding special characters with \ when included in a string) are necessary.

Your regex would then match a dot which would match any character making for example a valid because the preceding [0-9]{0,900} matches zero - 900 times.

Your regex would become:

var re = new RegExp("^[+-]?[0-9]{0,900}(?:\\.[0-9]{0,900})?$");

To match negative and positive decimal numbers that should not start with a dot, you could use:

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

Which will match the beginning of the string ^, an optional [+-]?, one or more digits [0-9]+ followed by an optional part which will match a dot and one or more digits (?:\.[0-9]+)? and then the end of the string $.

var re = new RegExp("^-?[0-9]+(?:\\.[0-9]+)?$");

var re = new RegExp("^[+-]?[0-9]+(?:\\.[0-9]+)?$");
var strings = [
  "1",
  "1.2",
  "0.232",
  ".232",
  "-1.2",
  "+1.2"

];

strings.forEach((s) => {
  console.log(s + " ==> " + re.test(s));
});

look here https://regex101.com/r/OREez0/1, in your function works but using react onChange doesnt work — Javier, May 03 '18 at 09:36
@JaviLesPaul Perhaps [this page](https://stackoverflow.com/questions/40883057/use-regular-expression-in-jsx-file-in-react-material-ui) can be helpful. — The fourth bird, May 03 '18 at 13:44

score 0 · Answer 2 · answered May 03 '18 at 08:15

0

I use this:

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

only numbers
positive and negative
dont allow .232

answered May 03 '18 at 08:15

Matias Pons

3
3

you can shorten `[0-9]\d*` to `\d+`. OP also wanted to allow a leading `+`, so you might as well allow that – Chrᴉz remembers Monica May 03 '18 at 08:47

Regular Expression for negative and positive decimal numbers

2 Answers2