The core library for managing forms with Preact Signals.

Features

TypeScript - Written in TypeScript with full type support for optimal DX.
Reactivity - Reactivity without abstractions thanks to Preact Signals.
Validation - Built-in validation support, including adapters for validation schema libraries.
Transformations - Transform values for the specific needs of your input fields.
Field Groups - Group fields together to manage parts of a form independently.
Async Data - Easily manage async initialisation, validation and submission.
Arrays + Dynamic Objects - Utilize arrays and dynamic objects within your forms.

Install

npm install @formsignals/form-core

If you have not installed signals, you will need to install it as well:

npm install @preact/signals-core

Create a new form instance:

const form = new FormLogic({
  defaultValues: {
    name: '',
    email: '',
  },
});

Then get a field instance from the form and configure it:

const nameField = form.getOrCreateField('name', {
  validate: (value) => {
    if (!value) {
      return 'Name is required';
    }
  },
});

Now you can interact with the field:

nameField.handleChange('John Smith');

You can also access the underlying signal directly:

const nameLength = computed(() => nameField.value.length);