Form actions menangani form submission di server — tanpa perlu API endpoint terpisah.

Membuat Action

// src/routes/login/+page.server.js
export const actions = {
  default: async ({ request }) => {
    const data = await request.formData()
    const email = data.get("email")
    const password = data.get("password")

    // validasi dan login
    if (!email) return { success: false, error: "Email wajib diisi" }

    // redirect setelah login
    throw redirect(303, "/dashboard")
  }
}

Form di Page

<!-- +page.svelte -->
<script>
  export let form
</script>

{#if form?.error}
  <p class="error">{form.error}</p>
{/if}

<form method="POST">
  <input name="email" type="email" />
  <input name="password" type="password" />
  <button>Login</button>
</form>

Form actions menggunakan progressive enhancement — bekerja tanpa JavaScript!