sveltekit-auth-cookies/src/routes/auth/register/index.svelte

<script type="ts">
  import {send} from '$lib/api';

  export let error: string;
  export let success: string;

  async function register(event: SubmitEvent) {
    error = ''

    const formEl = event.target as HTMLFormElement
    const response = await send(formEl)

    if (response.error) {
      error = response.error
    }

    if (response.success) {
      success = response.success
    }

    formEl.reset()
  }
</script>

<form on:submit|preventDefault={register} method="post" autocomplete="off">
  <div>
    <label for="username">Username
      <input id="username" name="username" type="text" required />
    </label>
  </div>
  <div>
    <label for="password">Password
      <input id="password" name="password" type="password" required />
    </label>
  </div>

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

  {#if success}
    <div>
      <p>Thank you for signing up!</p>
      <p><a href="/auth/login">You can log in.</a></p>
    </div>
  {/if}

  <button type="submit">Sign Up</button>
</form>

<style>
  .error {
    color: tomato;
  }
</style>