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Development Basics with Vanilla JS

Now that you've setup your project, it's time to give it a test run in the browser.

If you haven't started Vite in the terminal, do so now:

npm run dev

Install the extension

When the build completes, open Chrome or Edge and navigate to chrome://extensions. Make sure to turn on the developer mode switch.

Chrome developer mode switchEdge developer mode switch
Located in top right cornerLocated in left sidebar

Drag your dist folder into the Extensions Dashboard to install it. Your extension icon will be in the top bar. The icon will be the first letter of the extension's name.

Vite CRXJS Chrome Extension Action Context Menu with "Inspect pop-up window" highlighted

Inspect the popup

Once you've found the extension icon, right-click it and choose "Inspect popup window". This menu item will open the popup and the popup dev tools window. We need to inspect the popup to keep it open while making changes.

Vite CRXJS Chrome Extension Popup

Vite HMR for JavaScript

Let's see how Vite handles JavaScript updates without an HMR framework. We can add a counter button to test how Vite preserves the page state.

import './style.css'

document.querySelector('#app').innerHTML = `
<h1>Hello Vite!</h1>
<a href="" target="_blank">Documentation</a>
<button>Count: 0</button>

let count = 0
const button = document.querySelector('#app button')
button.addEventListener('click', () => {
button.textContent = `Count: ${count}`

Vite will trigger a full page reload when we save our file. The popup will stay open since the devtools inspector is open. Our button is there, but the elements look a little squashed.

Vite CRXJS Chrome Extension Popup

Vite HMR for CSS

HTML and JS changes trigger full page reloads, but Vite provides HMR updates for imported styles without a full page reload. Click that counter a few times and then update styles.css to fix the page layout.

#app {
font-family: Avenir, Helvetica, Arial, sans-serif;
text-align: center;
color: #2c3e50;
margin-top: 60px; /* Remove this line */

width: 100px;
display: flex;
flex-direction: column;
justify-content: center;
align-items: center;
row-gap: 5px;

Vite will update the styles while preserving the counter state. Pretty good for a vanilla JavaScript project!

Vite CRXJS Vanilla Popup with CSS update