use replace to remove chars not existing in a regex match

Question

I'am trying to allow following pattern for a single html input box with javascript regex

-int (aka any minus number so long it not followed by a zero and is in the first position)
0 (a single zero is allowed)
int (is allowed)

I use this function the remove anything that doesn't match it

    $('.dointcheck').live('keyup',
        function () {
            $(this).val($(this).val().replace((/^((?!:([1-9-]?[0-9])).)/g), ''));
            if ($(this).val().length == 0) {
                $(this).val(0);
            }
        });

which doesn't work. Other examples is:

/[^-0-9]/g it removes any non valid chars but doesnt check if the minus is the beginning and is followed by a zero. It allows minus everywhere in the string
(/^((?!:([1-9-]?[0-9])).)/g Don't allow none.
[^1-9-]?[^0-9]* Allow all...

I think I'am missing something.. Any suggestions would be most appreciated..

.live() has been deprecated with v1.7 and removed in v1.9

Andreas
– Andreas

2022-04-07 13:49:48 +00:00
Commented Apr 7, 2022 at 13:49 — Andreas
– Andreas, Commented Apr 7, 2022 at 13:49
<input type="number" ... />

Andreas
– Andreas

2022-04-07 13:50:20 +00:00
Commented Apr 7, 2022 at 13:50 — Andreas
– Andreas, Commented Apr 7, 2022 at 13:50

Hao Wu · Accepted Answer · 2022-04-07 14:30:06Z

1

You may try this regex

^(0).*|^(-?)([1-9]\d*)?.*|^.*

and replace it with $1$2$3 after input

document.querySelector('input').addEventListener('input', ({ target }) => target.value = target.value.replace(/^(0).*|^(-)?([1-9]\d*)?.*|^.*/g, '$1$2$3'));

<input />

It has three tests:

^(0).*               // if it starts with 0, discard everything after it
^(-)?([1-9]\d*)?.*   // otherwise it can only starts with a -, or any number that is not a 0. Then followed by other digits, then discard everything after it
^.*                  // if previous rules are not matched, discard everything

In short:

generally only -, 0-9 are allowed.
if you type a 0 first, nothing will be allowed after.
if you type a 1-9 first, only numbers are allowed after.
if you type a - first, only 1-9 is allowed next, then any digit is allowed after.

edited Apr 7, 2022 at 14:30

answered Apr 7, 2022 at 14:24

Hao Wu

21.6k7 gold badges37 silver badges79 bronze badges

Sign up to request clarification or add additional context in comments.

1 Comment

Jerker Pihl Over a year ago

This is was I needed and the explanation what everything does is extremly helpfull

Wraithdev3 · Accepted Answer · 2022-04-07 13:59:19Z

1

I changed your regexp and made it a bit more modular and it worked fine.

function toValidNumber(int) {
  return (/^\s*[+-]?(\d+|\d*\.\d+|\d+\.\d*)([Ee][+-]?\d+)?\s*$/).test(int) ? int : 0;
}

$('.dointcheck').live('keyup',
  function () {
    $(this).val(toValidNumber($(this).val()));
  });

Orginal RegEXP in Stackoverflow

answered Apr 7, 2022 at 13:59

Wraithdev3

391 silver badge6 bronze badges

Collectives™ on Stack Overflow

use replace to remove chars not existing in a regex match

2 Answers 2

1 Comment

Comments

Your Answer

Linked

Hot Network Questions

Collectives™ on Stack Overflow

2 Answers 2

1 Comment

Comments

Your Answer

Sign up or log in

Post as a guest

Linked

Related