Adding page progress bar to svelteKit

Adding a progress bar to your SPA or Transitional Application can significantly impact the user. For example, a fast-finishing progress bar can signal how fast the page work. The faster experience, the more likely the user will spend time on your website. In case your website is slow, it can give a message like ❝it’s working but need more time to load❞.

Let’s see how to add a page progress bar to your sveltekit application. We’ll be using nprogress to do so.

Basic Setup

Assuming you have a basic sveltekit project setup using npm init svelte@next, let’s add a __layout.svelte and about.svelte routes to the project.

<nav>
	<a href="/">Index</a>
	<a href="/about">About</a>
</nav>

<slot />

<h1>About page</h1>

Installing NProgress

npm i -D nprogress

Adding Progress Bar

We will use the $app/stores module for our progress bar. Specifically, the $navigating store.

navigating is a readable store. When navigating starts, its value is { from, to }, where from and to both mirror the page store value. When navigating finishes, its value reverts to null - Official docs.

Update the __layout.svelte like so:

<script>
	import NProgress from 'nprogress';
	import { navigating } from '$app/stores';

	// NProgress css
	import 'nprogress/nprogress.css';

	NProgress.configure({
		// Full list: https://github.com/rstacruz/nprogress#configuration
		minimum: 0.16
	});

	$: {
		if ($navigating) {
			NProgress.start();
		}
		if (!$navigating) {
			NProgress.done();
		}
	}
</script>

<nav>
	<a href="/">Index</a>
	<a href="/about">About</a>
</nav>

<slot />

Notice the $: { ... } declaration. It is a reactive declaration is svelte. Every time something in the page changes, the code block runs.

Before testing out your app, navigate to dev tools and set the page to load from a slow connection.

For some reason your throttling is not working, (I used stackblitz and it wasn’t working for me), add the following to any of your pages.

<script context="module">
	export async function load() {
		await new Promise((resolve) => setTimeout(resolve, 2000));
		return {
			props: {}
		};
	}
</script>

Basically, it creates a 2-second delay in the pages where it is added. Go back to your application and test it out.

Demo

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