Core of https://github.com/msafi/text-mask


8,0562990.8.05 years ago6 years agoMinified + gzip package size for @msafi/text-mask-core in KB


Text Mask Core

This module contains the core functions that power Text Mask. Currently, Text Mask has a wrapper for React, which can be used directly.

However, Text Mask Core functions could be useful on their own. That's why they are published and documented here as a separate module.

Getting started

To download the script, use npm.

npm i @msafi/text-mask-core --save

Include it

After installing with npm, you could possibly do something like this from your index.html:

<script src="./node_modules/@msafi/text-mask-core/dist/textMaskCore.js"></script>

Including this file in your source code will expose the global object textMaskCore.

Or if you're using Node.js or a bundler such as webpack or Browserify, you can require textMaskCore as such:

var textMaskCore = require('@msafi/text-mask-core')

How to use

textMaskCore exposes three functions:

  • conformToMask
  • adjustCaretPosition
  • convertMaskToPlaceholder


The general idea is to take user input, conform it to your desired mask using conformToMask, and then apply the output of conformToMask to the value of the HTML input element. Once you do that however, the caret position will be lost. You can then use adjustCaretPosition to restore the caret to its proper position.

To learn more about how to do that, see the API documentation below:

API documentation


This function takes a mask (string), i.e. 11/11/1111, and returns a placeholder (string).

const placeholder = convertMaskToPlaceholder('11/11/1111')

placeholder // __/__/____

You can use this function to initialize an input element to a placeholder value.

conformToMask(userInput, mask, config)

This function takes three arguments:

  • userInput (string): the string value that you want to conform to the mask
  • mask (string): the mask to which you want the string to conform. You can find mask documentation here.
  • config (object): optional config object. See below for details

This function returns an object shaped as {output: 'someConformedString', meta: {...}}'.

output is gonna contain the conformed string. As for meta, it contains some meta data about the operation. This meta data is needed by adjustCaretPosition function, which is documented below.


The config object takes the following values

  • guide (boolean) (defaults to true): this tells conformToMask whether you want the conformed string to contain a guide or no. The guide is basically the placeholder character and the mask hard characters. For example, with mask (111) 111-1111, input 123 with guide set to true would return (123) ___-____. With guide set to false, it would return (123) .

  • previousConformedInput (string) (required): this is the previous output of conformToMask. If you're calling conformToMask for the first time, pass this as an empty string or undefined.

  • placeholderCharacter (string): for documentation on this key, see this section of the component documentation page.

const results = conformToMask('5554833902', '(111) 111-1111')

results // {output: '(555) 483-3902', meta: {...some meta data}}

Whenever the value of the input element changes, you can pass that value to conformToMask and it'll make sure that the string looks like the given mask. You can then set that conformed string as the new value of the input element.


When you set the value of the input element, you lose the position of the caret. This function helps you restore the position.

adjustCaretPosition takes the following object of arguments:

  • previousConformedInput (string): the string value of the input before the last time you set its value. If you're calling this function for the first time, you can pass an empty string.
  • conformedToMaskResults (object): the return value of the last call to conformToMask
  • currentCaretPosition (integer): the position of the caret right before you called this function

adjustCaretPosition will return an integer representing the index of where the caret should be moved to next.


Public domain - CC0 1.0 Universal

If you find any bugs or have a feature request, please open an issue on github!

The npm package download data comes from npm's download counts api and package details come from npms.io.