The idea is a little Svelte component (check out the demo) that shows a cool progress bar, like what's on YouTube, or NProgress.

You can use it in your plain old web app, without bundling or anything, using the unpkg CDN:

<script src="https://unpkg.com/svelte-progress-bar/dist/ProgressBar.umd.js"></script>
<script>
	const progress = new ProgressBar({
		target: document.querySelector('body')
	})
	// start it on a page load
	progress.start()
	// complete it at some point in the future
	setTimeout(() => {
		progress.complete()
	}, 1000)
</script>

Or to include it in your web app:

import ProgressBar from 'svelte-progress-bar'
// or
const ProgressBar = require('svelte-progress-bar')
// then
const progress = new ProgressBar({
	target: document.querySelector('body')
})

Or if you are using the progress bar inside a Svelte template, you might use bind:this like this:

<script>
	import ProgressBar from 'svelte-progress-bar'
	let progress
</script>
<ProgressBar bind:this={progress} />
<!-- then somewhere later -->
<button on:click={() => progress.setWidthRatio(0.4)}>
	Set to 40% Width
</button>

If you were using a web app with a router, or some sort of page change event emitter, it might look like:

const router = // the page/state change event emitter
router.on('stateChangeStart', () => {
	progress.start()
})
router.on('stateChangeEnd', () => {
	progress.complete()
})

Or if you had some progress event emitter that actually told you the percent of progress, you might set the progress bar width manually with something like this:

const dataLoad = // some sort of data load progress event emitter
dataLoad.on('percentDone', percent => {
	progress.setWidthRatio(percent / 100) // must be a ratio
})
dataLoad.on('end', () => {
	progress.complete()
})

The progress bar does not have a default color, so you will need to set one. You can either set the color as a data property or override the CSS.

JavaScript:

const progress = new ProgressBar({
	target: document.querySelector('body'),
	props: { color: '#0366d6' }
})

Svelte component:

<ProgressBar color="#0366d6" />

Or in your CSS:

.svelte-progress-bar, .svelte-progress-bar-leader {
	background-color: #0366d6;
}
.svelte-progress-bar-leader {
	color: #0366d6;
}

If you are using some type of navbar at the top of the page, like Bootstrap's, it is likely that you will need to change the z-index to get the progress bar to appear over the navbar:

.svelte-progress-bar {
	z-index: 100;
}
.svelte-progress-bar-leader {
	z-index: 101;
}

You shouldn't need to play with these, they've been selected based on UX design expertise, but they're available if you need them:

• minimum (number, range: 0-1, default: 0.08): The starting percent width use when the bar starts. Starting at 0 doesn't usually look very good.
• maximum (number, range: 0-1, default: 0.994): The maximum percent width value to use when the bar is at the end but not marked as complete. Letting the bar stay at 100% width for a while doesn't usually look very good either.
• intervalTime (number, default: 800): Milliseconds to wait between incrementing bar width when using the start (auto-increment) method.
• settleTime (number, default: 700): Milliseconds to wait after the complete method is called to hide the progress bar. Letting it sit at 100% width for a very short time makes it feel more fluid.

These additional methods are available on an instantiated progress bar:

• start(): Set the width to the minimum and increment until maximum width.
• complete(): Set the width to 100% and then hide after settleTime.
• reset(): Set the width to minimum but do not start incrementing.
• animate(): Start incrementing from whatever the current width is.
• stop(): Stop incrementing and take no further action.
• setWidthRatio(ratio: number): Stop auto-incrementing and manually specify the width.

Published and released under the Very Open License.