Usage no npm install needed!

<script type="module">
  import formatInput from 'https://cdn.skypack.dev/format-input';
</script>

README

Format Input

Format user input as a date/credit card/etc.

npm install format-input --save

example

var formatInput = require('format-input');

formatInput(document.getElementById('#date-of-birth'), 'cc/cc/cccc');

Now enter the date 19/05/1985

When you type 190 it will be reformatted to 19/0

as you continue it will be reformatted until it reaches the end of the given format.

You can also supply a different separator, in fact you can use any character except for the placeholder which defaults to c if this conflicts with your format (or you just don't like the letter 'c' then you can change the placeholder to something else, like !. formatInput(element, '!!:!!, '!')