Masking a string

Question

I need to put a received string in this format:

"## ## ## ###" in typescript/javascript

Eg:

"12 34 56 789"

I know there's string-mask and some way via JQuery, is there a simplier way to do it?

score 42 · Accepted Answer · edited Apr 04 '22 at 14:20

42

You could replace each pattern part with the wanted data.

function format(value, pattern) {
    let i = 0;
    const v = value.toString();
    return pattern.replace(/#/g, _ => v[i++]);
}

console.log(format(123456789, '## ## ## ###'));

edited Apr 04 '22 at 14:20

Christian Vincenzo Traina

9,546
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answered Jul 11 '17 at 10:22

Nina Scholz

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this is really awesome and so short, love it. Thanks for sharing, I now use it :) – ghiscoding Jun 15 '18 at 18:15
@Nina Scholz What is the meaning of the underscore `(_)` character in the replace method? – Penny Liu Nov 30 '18 at 08:37
1

it is a unused variable, which is shorter to write than `() => v[i++]`, which is a function without parameter. the underscore is a variable. – Nina Scholz Nov 30 '18 at 08:39
@NinaScholz Thanks for your reply, but I got an unexpected result `23 45 67 89undefined` when the value is `023456789`. – Penny Liu Dec 01 '18 at 13:25
@Yi-TingLiu, for leading zero/es, you need to hand over a string insted of a number, because numbers does not have a leading zeroes. – Nina Scholz Dec 01 '18 at 14:53
Does this works on key up ? – CandleCoder May 19 '22 at 13:13
@CandleCoder, which keys? – Nina Scholz May 19 '22 at 13:23
Keyup event @NinaScholz – CandleCoder May 19 '22 at 14:54
@CandleCoder, if you add it to the event? why not? – Nina Scholz May 19 '22 at 14:55

score 1 · Answer 2 · answered Dec 16 '19 at 16:08

I needed one that masks any character with a "*", from the beginning or end of the string, so I wrote the following:

"use strict";

module.exports = {
  /**
   * @param {string} str
   * @param {string} maskChar
   * @param {number} unmaskedLength
   * @param {boolean} [maskFromStart]
   * @returns {string}
   */
  mask(str, maskChar, unmaskedLength, maskFromStart = true) {
    const maskStart = maskFromStart ? 0 : Math.max(0, unmaskedLength);
    const maskEnd = maskFromStart ? Math.max(0, str.length - unmaskedLength) : str.length;
    return str
      .split("")
      .map((char, index) => {
        if (index >= maskStart && index < maskEnd) {
          return maskChar;
        }
        else {
          return char;
        }
      })
      .join("");
  },
};

score 0 · Answer 3 · answered May 19 '22 at 14:58

0

The one which worked for me with the format xxx-xxx-xxxx with keyup event

stringOnKeyUp.replace(/^(\d{3})$/g, '$1-').replace(/^(\d{3}-\d{3})$/g, '$1-');

answered May 19 '22 at 14:58

CandleCoder

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Masking a string

3 Answers3

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