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Restricted Input

Allow restricted character sets in input elements.


Try the latest version of Restricted Input here.


  • Disallow arbitrary chars based on patterns
  • Maintains caret position
  • Format/Update on paste
  • Works in IE9+


Install dependencies

$ npm i

Watch files and run server

$ npm run development

This will start a server on port 3099 which can be overridden with the PORT env var.

Run tests

There are unit tests:

$ npm t


import RestrictedInput from 'restricted-input';
const formattedCreditCardInput = new RestrictedInput({
  element: document.querySelector('#credit-card'),
  pattern: '{{9999}} {{9999}} {{9999}} {{9999}}'


Patterns are a mixture of Placeholders and PermaChars.


A Placeholder is the part of the pattern that accepts user input based on some restrictions. A placeholder is defined in the pattern using two open curly brackets, the placeholder, followed by two closing curly brackets e.g. {{Abc123}}.

The patterns a Placeholder can be are:

  • a single alpha character that matches the alpha regex /[A-Za-z]/. e.g. {{C}} will match one alpha character.
  • a single digit that matches the digit regex /[0-9]/. e.g. {{3}} will match one digit.
  • a * character that matches /./. e.g. {{*}} will match the next character.


A PermaChar is the part of the pattern that is automatically inserted. PermaChars are defined in the pattern as any characters other than Placeholders.

Example patterns

Some example patterns with behavior are listed:

  • 12{{3}}
    • Inserts 12.
    • Waits for a single digit from the user.
  • {{A}}BC
    • Waits for a single alpha from the user.
    • Inserts BC.
  • ${{*2L}}E
    • Inserts $.
    • Waits for any single character input from the user.
    • Waits for a single digit from the user.
    • Waits for a single alpha from the user.
    • Inserts E.



Key Type Description
element HTMLInputElement or HTMLTextAreaElement A valid reference to an input or textarea DOM node
pattern String Pattern describing the allowed character set you wish for entry into corresponding field. See Patterns.

Browser Support


  • Chrome (latest)
  • Firefox (17+)
  • Safari (8+)
  • IE11 (desktop/metro)
  • IE10 (desktop/metro)
  • IE9

Browsers Where Formatting is Turned Off Automatically

Old versions of Samsung Android browsers are incompatible with formatting. These will not attempt to intercept the values and format the input.


  • Improve jsdoc
  • Add example guides/pages