@westbrookdaniel/form

A framework-agnostic form library that provides tools for validation and submission of forms.

Installation

npm install @westbrookdaniel/form

API

Form

The Form class provides methods for validating and handling form submissions.

Constructor

constructor({ fields, loose, form, defaultMessage }: Options<TFormData>)

• fields: An object containing field validators.
• loose: A boolean indicating whether to use loose validation.
• form: An array of form-level validators.
• defaultMessage: A function that returns the default error message for a field.

Methods

• validate(data: unknown): Promise<void>: Validates the form data.
• hasErrors(field?: keyof TFormData): boolean: Checks if there are any errors.
• handle<T = void>(fn: FormHandler<TFormData, T>): (e: SubmitEvent) => Promise<T>: Handles form submission.
• assert(): TFormData: Asserts that the form is valid and returns the form data.
• reset(): void: Resets the form state.
• subscribe(key: "fieldErrors" | "submitting" | "data" | "formError" | "isValid", callback: (value: any) => void): () => void: Subscribes to changes in form state.

Usage

Here's an example of how to use the form library:

import { Form } from "./index";

interface UserFormData {
  name: string | null;
  email: string;
  password: string;
}

const form = new Form<UserFormData>({
  fields: {
    name: [
      ({ name }) => typeof name !== "string",
      (form) => form.name === "" && (form.name = null),
      () => new Promise((r) => setTimeout(r, 1)),
    ],
    email: [
      ({ email }) => typeof email !== "string",
      ({ email }) => (email?.trim() ? null : "Required"),
      ({ email }) =>
        /^[^@]+@[^@]+\.[^@]+$/g.test(email ?? "") ? null : "Invalid email",
    ],
    password: [
      ({ password }) => typeof password !== "string",
      ({ password }) => (password?.trim() ? null : "Required"),
      ({ password }) => ((password?.length ?? 0) > 8 ? null : "> 8 characters"),
    ],
  },
  form: [
    ({ password, name }) =>
      name && password?.includes(name)
        ? "Password cannot contain your name"
        : null,
  ],
});

const submit = form.handle(async (formData, formElement) => {
  await form.validate(formData);

  if (form.hasErrors()) return;

  const data = form.assert();

  formElement.reset();

  console.log(data);
});

// ... An example using React of how to use this in a form ...

<form onSubmit={submit} noValidate>
  <label>
    Email
    <input name="email" type="email" />
    <span className="error">{form.fieldErrors.email}</span>
  </label>
  <label>
    Password
    <input name="password" type="password" />
    <span className="error">{form.fieldErrors.password}</span>
  </label>
  {form.submitting ? (
    <button disabled>Submitting...</button>
  ) : (
    <button>Submit</button>
  )}
</form>;

Vanilla JS Integration

Here's an example of how to use the form library with vanilla JavaScript:

import { Form } from "@westbrookdaniel/form";

const form = new Form({
  fields: {
    email: [
      ({ email }) => (email?.trim() ? null : "Required"),
      ({ email }) =>
        /^[^@]+@[^@]+\.[^@]+$/g.test(email ?? "") ? null : "Invalid email",
    ],
    password: [
      ({ password }) => (password?.trim() ? null : "Required"),
      ({ password }) => ((password?.length ?? 0) > 8 ? null : "> 8 characters"),
    ],
  },
});

const emailError = document.getElementById("email-error");
const passwordError = document.getElementById("password-error");
const submitButton = document.getElementById("submit-button");

form.subscribe("fieldErrors", (errors) => {
  emailError.textContent = errors.email || "";
  passwordError.textContent = errors.password || "";
});

form.subscribe("submitting", (submitting) => {
  submitButton.disabled = submitting;
  submitButton.textContent = submitting ? "Submitting..." : "Submit";
});

const handleSubmit = form.handle(async (formData) => {
  await form.validate(formData);

  if (form.hasErrors()) return;

  const data = form.assert();
  console.log(data);
});

document.querySelector("form").addEventListener("submit", handleSubmit);

This example demonstrates how to use the Form class with vanilla JavaScript, including subscribing to form state changes and handling form submission.

License

This project is licensed under the MIT License.