Media elements

Advanced Svelte / Advanced bindings

Part 2/ Advanced bindings/Media elements

You can bind to properties of <audio> and <video> elements, making it easy to (for example) build custom player UI, like AudioPlayer.svelte.

First, add the <audio> element along with its bindings (we'll use the shorthand form for src, duration and paused):

<div class="player" class:paused>
	<audio
		{src}
		bind:currentTime={time}
		bind:duration
		bind:paused
	/>

	<button
		class="play"
		aria-label={paused ? 'play' : 'pause'}
	/>

Next, add an event handler to the <button> that toggles paused:

<button
	class="play"
	aria-label={paused ? 'play' : 'pause'}
	on:click={() => paused = !paused}
/>

Our audio player now has basic functionality. Let's add the ability to seek to a specific part of a track by dragging the slider. Inside the slider's pointerdown handler there's a seek function, where we can update time:

function seek(e) {
	const { left, width } = div.getBoundingClientRect();

	let p = (e.clientX - left) / width;
	if (p < 0) p = 0;
	if (p > 1) p = 1;

	time = p * duration;
}

When the track ends, be kind — rewind:

<audio
	{src}
	bind:currentTime={time}
	bind:duration
	bind:paused
	on:ended={() => {
		time = 0;
	}}
/>

The complete set of bindings for <audio> and <video> is as follows — seven readonly bindings...

• duration (readonly) — the total duration, in seconds
• buffered (readonly) — an array of {start, end} objects
• seekable (readonly) — ditto
• played (readonly) — ditto
• seeking (readonly) — boolean
• ended (readonly) — boolean
• readyState (readonly) — number between (and including) 0 and 4

...and five two-way bindings:

• currentTime — the current position of the playhead, in seconds
• playbackRate — speed up or slow down (1 is 'normal')
• paused — this one should be self-explanatory
• volume — a value between 0 and 1
• muted — a boolean value where true is muted

Videos additionally have readonly videoWidth and videoHeight bindings.