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

Usage no npm install needed!

<script type="module">
  import textMaskCore from 'https://cdn.skypack.dev/text-mask-core';


Text Mask Core

This module contains the core functions that power Text Mask. Text Mask has wrappers for Angular1, Angular2, Ember, React and Vue 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 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/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('text-mask-core')

How to use

textMaskCore exposes three functions:

  • createTextMaskInputElement
  • conformToMask
  • adjustCaretPosition


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.

API documentation


This function takes a configuration and returns an object with an update method. The update method is used to conform the raw value to the mask you provide in the config.

// the config requires a `mask` and a reference to an `input` element.
const textMaskConfig = {inputElement, mask}

// initialize text mask
const textMaskInputElement = createTextMaskInputElement(textMaskConfig)

// call `update` to conform the `inputElement.value` to the provided `mask`.

The textMaskConfig requires a mask and a reference to the inputElement. See the documentation here for more information on the properties that the textMaskConfig accepts.

The default use-case is for the textMaskConfig to be passed to the createTextMaskInputElement method when you initialize Text Mask. However, you can also pass the value and textMaskConfig to the update method.

const textMaskConfig = {inputElement, mask}

// initialize text mask without a config (or with a default config)
const textMaskInputElement = createTextMaskInputElement()

// call `update` with the raw value and config
textMaskInputElement.update(inputElement.value, textMaskConfig)

The update method should be called every time the inputElement.value changes.

conformToMask(rawValue, mask, config)

This function takes three arguments:

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

This function returns an object with a property conformedValue (string).

const results = conformToMask('5554833902', ['(', /[1-9]/, /\d/, /\d/, ')', ' ', /\d/, /\d/, /\d/, '-', /\d/, /\d/, /\d/, /\d/])

results.conformedValue // '(555) 483-3902'


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 ['(', /[1-9]/, /\d/, /\d/, ')', ' ', /\d/, /\d/, /\d/, '-', /\d/, /\d/, /\d/, /\d/], input 123 with guide set to true would return (123) ___-____. With guide set to false, it would return (123) .

  • previousConformedValue (string) (required): this is the previous output of conformToMask. If you're calling conformToMask for the first time, you don't have to pass this value.

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

const results = conformToMask('5554833902', ['(', /[1-9]/, /\d/, /\d/, ')', ' ', /\d/, /\d/, /\d/, '-', /\d/, /\d/, /\d/, /\d/])

results.conformedValue // '(555) 483-3902'

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:

  • previousConformedValue (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.
  • conformedValue (string): the conformedValue returned from the last call to conformToMask
  • currentCaretPosition (integer): the position of the caret right before you called this function
  • rawValue (string): value of the input element
  • placeholderChar (string): placeholder character
  • placeholder (string): the generated placeholder
  • indexesOfPipedChars (array): an array of piped characters returned from the last call to the pipe function
  • caretTrapIndexes (array): an array of caret trap indexes

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