Is it possible to replace digits in a string with the same digits with leading zeros using regex

Question

Say I have a string "abc123def45"

Is it possible, with javascript regex to replace all the numbers in the string to be either the same length or all at a fixed length of, say, 6 digits.

So, if going for the 6 digits approach, the resulting string would be "abc000123def000045"

And if going for the same length approach (which I suspect will be harder if not impossible with regex), the resulting string would be "abc123def045"

I can certainly find all the numbers with regex with something like:

\d+

but how do I get the right amount of leading zeros in the replacement?

Sample code:

var s = "abc123def45";
var r = s.replace(/\d+/g, "000123"); // this is wrong of course

Do you want to use a regex for a particular reason? Or you want a solution and so far regex is the only way you think it's possible? — AD7six, May 08 '14 at 09:46
I already have a solution, but wanted to use regex to be more succinct and supposedly more efficient — Graham, May 08 '14 at 10:51

score 3 · Accepted Answer · answered May 08 '14 at 09:50

3

You can use:

var s = "abc123def45";
var r = s.replace(/\d+/g, function($0) {
      return new Array(6-$0.length+1).join('0')+$0; });
//=> "abc000123def000045"

answered May 08 '14 at 09:50

anubhava

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Brilliant, didn't know about functions as the replacement option – Graham May 08 '14 at 10:45

score 2 · Answer 2 · answered May 08 '14 at 09:46

I can't think of a way that doesn't use a function as a callback in replace, e.g.:

var zeros = "0000000000";
var r = s.replace(/\d+/g, function(m) {
    return zeros.substring(0, 6 - m.length) + m;
});

Complete example: Live Copy

<!DOCTYPE html>
<html>
<head>
<meta charset=utf-8 />
<title>Zero Padding with RegEx</title>
</head>
<body>
  <script>
    (function() {
      "use strict";

      var s = "abc123def45";
      var zeros = "0000000000";
      var r = s.replace(/\d+/g, function(m) {
        return zeros.substring(0, 6 - m.length) + m;
      });
      display("Result: " + r);

      function display(msg) {
        var p = document.createElement('p');
        p.innerHTML = String(msg);
        document.body.appendChild(p);
      }
    })();
  </script>
</body>
</html>

Is it possible to replace digits in a string with the same digits with leading zeros using regex

2 Answers2