Loading timers

It’s important that users understand that things are happening when they submit a form. Loading timers can be used to provide feedback when there is a server response delay, for example by displaying a loading spinner icon.

Usage

const { form, enhance, submitting, delayed, timeout } = superForm(data.form, {
  delayMs?: 500
  timeoutMs?: 8000
})

delayMs should be positive and always smaller than or equal to timeoutMs, otherwise the timer behavior will be undefined. And of course, the Superforms use:enhance must be added to the form element, since this is client-side behavior.

Submit state

After a certain time when the form is submitted, determined by delayMs and timeoutMs, the timers changes state. The states are:

Idle → submitting → delayed → timeout
       0 ms         500 ms    8000 ms

These states affect the readable stores submitting, delayed and timeout, returned from superForm. They are not mutually exclusive, so submitting won’t change to false when delayed becomes true.

Loading indicators

A perfect use for these timers is to show a loading indicator while the form is submitting:

src/routes/+page.svelte

<script lang="ts">
  const { form, errors, enhance, delayed } = superForm(data.form);
  import spinner from '$lib/assets/spinner.svg';
</script>

<form method="POST" use:enhance>
  <button>Submit</button>
  {#if $delayed}<img src={spinner} />{/if}
</form>

The reason for using delayed instead of submitting is based on the article Response Times: The 3 Important Limits, which states that for short waiting periods, no feedback is required except to display the result. Therefore, delayed is used to show a loading indicator after a little while, not instantly.

Visualizing the timers

Submit the following form and play around with the different settings. Different loading spinners are set to display when delayed and timeout are true respectively.

The default multipleSubmits setting prevents the form from being submitted multiple times, until the timeout state is reached. Click multiple times to see the effect of that.

Idle → submitting → delayed → timeout
       0 ms         500 ms    2000 ms

By experimenting with the timers and the delay between them, it’s certainly possible to prevent the feeling of unresponsiveness.