Mask Plugin

Alpine's Mask plugin allows you to automatically format a text input field as a user types.

This is useful for many different types of inputs: phone numbers, credit cards, dollar amounts, account numbers, dates, etc.

Installation

You can use this plugin by either including it from a <script> tag or installing it via NPM:

Via CDN

You can include the CDN build of this plugin as a <script> tag, just make sure to include it BEFORE Alpine's core JS file.

<!-- Alpine Plugins -->
<script defer src="https://cdn.jsdelivr.net/npm/@alpinejs/[email protected]/dist/cdn.min.js"></script>
 
<!-- Alpine Core -->
<script defer src="https://cdn.jsdelivr.net/npm/[email protected]/dist/cdn.min.js"></script>

Via NPM

You can install Mask from NPM for use inside your bundle like so:

npm install @alpinejs/mask

Then initialize it from your bundle:

import Alpine from 'alpinejs'
import mask from '@alpinejs/mask'
 
Alpine.plugin(mask)
 
...

x-mask

The primary API for using this plugin is the x-mask directive.

Let's start by looking at the following simple example of a date field:

<input x-mask="99/99/9999" placeholder="MM/DD/YYYY">

Notice how the text you type into the input field must adhere to the format provided by x-mask. In addition to enforcing numeric characters, the forward slashes / are also automatically added if a user doesn't type them first.

The following wildcard characters are supported in masks:

Wildcard Description
* Any character
a Only alpha characters (a-z, A-Z)
9 Only numeric characters (0-9)

Dynamic Masks

Sometimes simple mask literals (i.e. (999) 999-9999) are not sufficient. In these cases, x-mask:dynamic allows you to dynamically generate masks on the fly based on user input.

Here's an example of a credit card input that needs to change it's mask based on if the number starts with the numbers "34" or "37" (which means it's an Amex card and therefore has a different format).

<input x-mask:dynamic="
    $input.startsWith('34') || $input.startsWith('37')
        ? '9999 999999 99999' : '9999 9999 9999 9999'
">

As you can see in the above example, every time a user types in the input, that value is passed to the expression as $input. Based on the $input, a different mask is utilized in the field.

Try it for yourself by typing a number that starts with "34" and one that doesn't.

x-mask:dynamic also accepts a function as a result of the expression and will automatically pass it the $input as the first parameter. For example:

<input x-mask:dynamic="creditCardMask">
 
<script>
function creditCardMask(input) {
    return input.startsWith('34') || input.startsWith('37')
        ? '9999 999999 99999'
        : '9999 9999 9999 9999'
}
</script>

Money Inputs

Because writing your own dynamic mask expression for money inputs is fairly complex, Alpine offers a prebuilt one and makes it available as $money().

Here is a fully functioning money input mask:

<input x-mask:dynamic="$money($input)">

If you wish to swap the periods for commas and vice versa (as is required in certain currencies), you can do so using the second optional parameter:

<input x-mask:dynamic="$money($input, ',')">

You may also choose to override the thousands separator by supplying a third optional argument:

<input x-mask:dynamic="$money($input, '.', ' ')">

You can also override the default precision of 2 digits by using any desired number of digits as the fourth optional argument:

<input x-mask:dynamic="$money($input, '.', ',', 4)">
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