Trap Plugin
Alpine's Trap plugin allows you to conditionally trap focus inside an element.
This is useful for modals and other dialog elements.
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 --> <!-- Alpine Core -->
Via NPM
You can install Trap from NPM for use inside your bundle like so:
npm install @alpinejs/trap
Then initialize it from your bundle:
import Alpine from 'alpinejs'import trap from '@alpinejs/trap' Alpine.plugin(trap) ...
x-trap
The primary API for using this plugin is the x-trap
directive.
x-trap
accepts a JS expression. If the result of that expression is true, then the focus will be trapped inside that element until the expression becomes false, then at that point, focus will be returned to where it was previously.
For example:
<div x-data="{ open: false }"> <button @click="open = true">Open Dialog</button> <span x-show="open" x-trap="open"> <p>...</p> <input type="text" placeholder="Some input..."> <input type="text" placeholder="Some other input..."> <button @click="open = false">Close Dialog</button> </span></div>
Nesting dialogs
Sometimes you may want to nest one dialog inside another. x-trap
makes this trivial and handles it automatically.
x-trap
keeps track of newly "trapped" elements and stores the last actively focused element. Once the element is "untrapped" then the focus will be returned to where it was originally.
This mechanism is recursive, so you can trap focus within an already trapped element infinite times, then "untrap" each element successively.
Here is nesting in action:
<div x-data="{ open: false }"> <button @click="open = true">Open Dialog</button> <span x-show="open" x-trap="open"> ... <div x-data="{ open: false }"> <button @click="open = true">Open Nested Dialog</button> <span x-show="open" x-trap="open"> ... <button @click="open = false">Close Nested Dialog</button> </span> </div> <button @click="open = false">Close Dialog</button> </span></div>
Modifiers
.inert
When building things like dialogs/modals, it's recommended to hide all the other elements on the page from screenreaders when trapping focus.
By adding .inert
to x-trap
, when focus is trapped, all other elements on the page will receive aria-hidden="true"
attributes, and when focus trapping is disabled, those attributes will also be removed.
<!-- When `open` is `false`: --><body x-data="{ open: false }"> <div x-trap.inert="open" ...> ... </div> <div> ... </div></body> <!-- When `open` is `true`: --><body x-data="{ open: true }"> <div x-trap.inert="open" ...> ... </div> <div aria-hidden="true"> ... </div></body>
.noscroll
When building dialogs/modals with Alpine, it's recommended that you disable scrollling for the surrounding content when the dialog is open.
x-trap
allows you to do this automatically with the .noscroll
modifiers.
By adding .noscroll
, Alpine will remove the scrollbar from the page and block users from scrolling down the page while a dialog is open.
For example:
<div x-data="{ open: false }"> <button>Open Dialog</button> <div x-show="open" x-trap.noscroll="open"> Dialog Contents <button @click="open = false">Close Dialog</button> </div></div>
Notice how you can no longer scroll on this page while this dialog is open.
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