Regex in javascript in a very specific format

Question

I have a input that has to format what's the user typing(actually it is info from his bank account). But the numbers have to be formatted in a certain way:

the first 5 digits must be numbers.
if the user type more than 5 numbers, the last number must have a '-' before it
after the 5 digit, the user can type 'x' or 'X'
the number can have minimun of 5 digits, and maximum of 15

examples:

12345
12345-1
123456-1
1234567-1
12345-x
123456789-x
123456789-X
12345678901234-5

Actually I'm using a normalizer that replaces the string.

This is what I'm using but I cant format it correctly.

export const normalizeBankAccount = value => {
    if (!value) {
      return value
    }

    if(value.length <= 16 && (!value.match(/[^\d|X]/g) || !value.match(/[^\d|-]/g) || !value.match(/[^\d|x]/g))) {
      if(value.length <= 5){
        return value.replace(/[^\d]/g, '')
      } else if(value.length >= 6) {
        const len = value.length;
        const aux=value;
        const initial = value.substring(0,value.length-1).replace('-', '');
        console.log("len: " +len, "\naux: " +aux,"\ninitial: "+ initial)
        return value.replace(new RegExp("\\d{"+ len +"}") , initial+ '-').replace(/[X]/g, '-X').replace(/[x]/g, '-x')
      }
    }
}

When I use this method, the string is formatted like this:

12345-6789123

Nina Scholz · Accepted Answer · 2019-04-13 16:08:19Z

3

You could look for a given length, followed by a single character and add a minus sign.

const
    normalize = string => string.replace(/^\d{5,14}(?=[0-9x]$)/i, '$&-');

console.log(['12345', '123451', '1234561', '12345671', '12345x', '123456789x', '123456789X', '123456789012345'].map(normalize));

Example with input.

function update(element) {
    element.value = element.value
        .replace(/[^0-9x]/gi, '')
        .replace(/x(?=.)/gi, '')
        .replace(/^\d{5,14}(?=[0-9x]$)/i, '$&-');
}

<input type="text" onkeyup="update(this)" id="x">

edited Apr 13, 2019 at 16:08

answered Apr 13, 2019 at 14:49

Nina Scholz

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10 Comments

Ramon Over a year ago

It actually don't work because the numbers must be formatted as the user keeps typing

Nina Scholz Over a year ago

you need to clean the string from all minus signs and apply the normalization.

Ramon Over a year ago

Almost working, I removed the minus sign as you said like this: ` string.replace('-', '').replace(/^\d{5,14}(?=[0-9x]$)/i, '$&-') ` But I cant type x or X

Nina Scholz Over a year ago

the replace with a string, instead of a regular expression replace only the first occurence of the find. the version with a regex and a global flag searches for all occurences.

Nina Scholz Over a year ago

you could remove unwanted characters. maybe you need another check for shorter items with 'x'.

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