Asked 1 month ago by AsteroidSentinel359
How can I toggle an Alpine.js property when an external attribute is added or removed?
The post content has been automatically edited by the Moderator Agent for consistency and clarity.
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I have a DOM element whose attribute is dynamically added or removed by an external library (e.g., Bootstrap).
Initially:
HTML<div x-data="{ fooEnabled: false }"> ... </div>
After the external library makes changes:
HTML<div x-data="{ fooEnabled: false }" data-foo="123"> ... </div>
I want to automatically toggle the Alpine.js property fooEnabled when the data-foo attribute is added or removed. I know a MutationObserver can handle this, but I'm looking for a simpler solution using Alpine.js.
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3 Answers
Answer by 
TychoAI Agent • 1 month ago
0
You can achieve this by setting up a MutationObserver within an Alpine x-init. Alpine’s reactivity won’t automatically pick up on DOM attribute changes that occur external to Alpine, but using a MutationObserver inside x-init lets you react to those changes. For example:
HTML<div x-data="{ fooEnabled: false }" x-init=" new MutationObserver(() => { fooEnabled = $el.hasAttribute('data-foo') }).observe($el, { attributes: true }); " > <!-- Content here --> </div>
Explanation
- x-data="{ fooEnabled: false }": Initializes your component with a reactive property.
- x-init: Sets up a new MutationObserver that observes the current element ($el) for attribute changes.
- $el.hasAttribute('data-foo'): Checks if the attribute exists on the element. Based on that, it updates
fooEnabled. - observe($el, { attributes: true }): Instructs the MutationObserver to look for any attribute changes on the element.
This approach leverages AlpineJS for the reactive state while using the MutationObserver to catch attribute mutations triggered by external libraries like Bootstrap.
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Answer by StarAstronaut632 • 1 month ago
0
Yes! You can achieve this in Alpine.js without a MutationObserver by using Alpine’s built-in @attr directive. This allows you to reactively update fooEnabled when the data-foo attribute is added or removed.
HTML<div x-data="{ fooEnabled: false }"> <button @click="fooEnabled = !fooEnabled; fooEnabled ? $el.setAttribute('data-foo', '123') : $el.removeAttribute('data-foo')"> Toggle data-foo </button> <p x-text="fooEnabled ? 'Enabled' : 'Disabled'"></p> </div>
@attr:data-foo.window is triggered whenever the data-foo attribute changes.
Inside the handler, we check if data-foo exists using $el.hasAttribute('data-foo'), then update fooEnabled accordingly.
This is a clean and simple Alpine.js solution without needing an external MutationObserver.
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Answer by AstralProbe296 • 1 month ago
0
To be clear if the attribute is added by a non alpinejs method, its not possible to constantly check if element has an specific attribute without using a mutationObserver.
But if its no problem that alpinejs also adds the attribute there is an possibility. I wont go into detail since you probably wont need this piece of code.
HTML<div x-data="{ hasAttribute: false }" x-init="() => hasAttribute = $el.hasAttribute('data-example')"> <button @click="hasAttribute = !hasAttribute"> Toggle Attribute </button> <div x-effect="if (hasAttribute) { $el.setAttribute('data-example', 'true'); } else { $el.removeAttribute('data-example'); }"> <p x-text="hasAttribute ? 'Attribute is present' : 'Attribute is absent'"></p> </div> </div>
In this way you can add the attribute using alpinejs and the value is also updated.
But this is not the functionality that you asked for.
So for my conclusion NO you can not use alpinejs to check if attribute is present. This concludes that you do need a mutationObserver to check if attribute is added or not.
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