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If you are not yet familiar with working on forms with Alpine.js, you can refresh your knowledge in our first article on this topic, Interactive forms with Alpine.js.
In our first article on interactive forms with Alpine.js, we already indicated that Alpine.js can also be used to influence individual elements in addition to the general display of server-side information in the form.
Due to the popular demand, we have decided to take up precisely this topic in this follow-up article and show examples of how you can use information and states to validate a form with Alpine.js.
SetupDownload Astro Boilerplate
If our boilerplate isn’t right for you, that’s not a problem. The steps for validating form entries work in any project with Alpine.js.
Integrating methods for Alpine.js
In order to be able to access the required data and methods from Alpine.js in the further course of the implementation, these are first declared in order to avoid errors in the further course.
form() controls the
loading state and saves the
Response sent by the server via the
submit() method, which is executed when the form is submitted.
fakeResponse() is also included, which “receives” exemplary and simplified validation errors from our fictitious backend.
Response must contain an
error object in which each key-value pair consists of the name of the input element and the associated validation error.
input.ts handles the display of validation errors for an input element via the
validate() method, which is integrated via the
x-effect attribute in order to recalculate the data for display when the form is submitted.
Finally, the methods declared for Alpine.js are imported for this step and registered in the EventListener
alpine:init in order to be able to access the required scopes.
Declaring optional utility methods
So that we can also use names for input elements as labels, we create the method
capitalize, which splits strings written in kebab-case (e.g.:
"email-address") and capitalises each word.
If you decide against capitalisation, the corresponding references in the
input.astrocomponent must be removed
Creating pages and components in Astro
In the following step, we create the pages and components we need for the form. We define an
<Input /> component and integrate it into the form block.
input.astro combines the elements
<input /> and
<label> in one component and also contains the representation of the validation errors, which are mapped via the Alpine context
index.astro represents our form block and uses the predefined component
<Input /> and supplements its logic with the
form context so that errors from the
response object can be displayed.
While our component
<Input /> handles the display of validation errors, we bind the
disabled attribute of the individual input elements to the
loading state in order to prevent multiple submissions of the form during processing.
With Alpine.js, we demonstrate how validation errors from the backend are dynamically displayed in a form and how input elements react to corresponding events in the browser.