parse.md

title	Parse form requests
description	Server-side form validation with Simple Form using validateForm() and Astro.locals.form helpers. Parse and validate FormData with Zod schemas.
sidebar	order 2

:::caution ⚠️ This package is no longer maintained. Astro now has Server Islands, which largely replace the use cases explored by this package. Server Islands also offer a simpler mental model for streaming content that scales to a number of deployment hosts.

That said, if you want to understand how this package works to fork the functionality for your own use, watch my YouTube walkthrough! :::

Simple form exposes helpers to parse and validate form requests with generic APIs and the Astro.locals.form object when using Astro frontmatter.

validateForm()

Type: validateForm<T extends ZodRawShape>(params: { formData: FormData, validator: T): Promise<GetDataResult<T>>

The validateForm() function can be used to validate any form request using a simple form validator. This returns data parsed by your validator or a fieldErrors object:

import { validateForm, createForm } from 'simple:form';

const signup = createForm(...);

const parsed = await validateForm({ formData, validator: signup.validator });
if (parsed.data) {
  console.info(parsed.data);
}

Astro.locals.form

Simple form exposes helpers to parse form requests from your Astro frontmatter.

getData()

Type: getData<T extends { validator: FormValidator }>(form: T): Promise<GetDataResult<T["validator"]> | undefined>

Astro.locals.form.getData() parses any incoming form request with the method POST. This will return undefined if no form request was sent, or return form data parsed by your Zod validator.

If successful, result.data will contain the parsed result. Otherwise, result.fieldErrors will contain validation error messages by field name:

---
import { z } from 'zod';
import { createForm } from 'simple:form';

const checkout = createForm({
  quantity: z.number(),
});

const result = await Astro.locals.form.getData(checkout);

if (result?.data) {
  console.log(result.data);
  // { quantity: number }
}
---

<form method="POST">
  <label for="quantity">Quantity</label>
  <input id="quantity" {...checkout.inputProps.quantity} />
  {
    result?.fieldErrors?.quantity?.map(error => (
      <p class="error">{error}</p>
    ))
  }
  ...
</form>

getDataByName()

Type: getDataByName<T extends { validator: FormValidator }>(name: string, form: T): Promise<GetDataResult<T["validator"]> | undefined>

You may have multiple forms on the page you want to parse separately. You can define a unique form name in this case, and pass the name as a hidden input within the form using <FormName>:

---
import { z } from 'zod';
import { createForm } from 'simple:form';

const checkout = createForm({
  quantity: z.number(),
});

const result = await Astro.locals.form.getDataByName(
  'checkout',
  checkout,
);

if (result?.data) {
  console.log(result.data);
  // { quantity: number }
}
---

<form method="POST">
  <label for="quantity">Quantity</label>
  <input id="quantity" {...checkout.inputProps.quantity} />

  <FormName value="checkout" />
  <!--Renders the following hidden input-->
  <!--<input type="hidden" name="_formName" value="checkout" />-->
</form>