Regex for replacing first 5 numbers, irrespective of anything between them?

Question

I'm trying to achieve the following match

Input

123-45-6789
123456789
1234

Reg Ex(s) Tried with output:

\d{5}

123-45-6789

123456789

1234

\d{2,3}

123-45-6789

123456789

1234

\d{3}-{0,1}\d{2}

123-45-6789

123456789

1234

I need to supply this regex to replace method, and I don't want the "-" to be replaced, it should only replace the first 5 digits without changing the format:

Expected Output

123-45-6789

123456789

1234

EDIT

In the above sample outputs:

1> all are matched with global regex 2> the bolded digits are only expected to be matched

The Purpose

I need to mask SSN, eg: 444-55-6666 becomes ###-##-6666 and 444556666 becomes #####6666. Without hampering the format.

Answer 1

You want to match and replace those first five digits:

var str = `123-45-6789
123456789
1234
`
console.log(str.replace(/^(\D*\d\D*){5}/gm, function(match) {
    return match.replace(/\d/g, '*');
}))

Answer 2

Here's other ways of looking at it:

• You want to ignore all non-numeric characters, and then get the first five numbers

  input.replace(/\D/g,'').substr(0,5);
  

• You want to match five numeric characters, wherever they may appear in the input

  input.match(/\d/g).slice(0,5);
  

There is almost always more than one way to approach a problem. If you can't figure out how to do what you want, try re-wording the problem until you find something you can do.