For those of you not familiar with the world of web extension development, a storm is brewing with Chrome. Google will stop support for manifest version 2, which is what the vast majority of web extensions use. Manifest version 3 sees many changes but the largest change is moving from persistent background scripts to service workers. This…is…a…massive…change.
Changes from manifest version 2 to version 3 include:
- Going from persistent background script to a service worker that can die after 5 minutes
- No use of
<iframe>
elements or other DOM APIs from the service worker - All APIs have become Promise-based
- Restrictions on content from a CSP perspective
One function that web extensions often employ is executing scripts upon each new page load. For a web extension like MetaMask, we need to provide a global window.ethereum
for dApps to use. So how do we do that with manifest version 3?
As of Chrome v102, developers can define a world
property with a value of isolated
or main
(in the page) for content scripts. While developers should define content_scripts
in the extension’s manifest.json
file, the main
value really only works (due to a Chrome bug) when you programmatically define it from the service worker:
await chrome.scripting.registerContentScripts([ { id: 'inpage', matches: ['http://*/*', 'https://*/*'], js: ['in-page.js'], runAt: 'document_start', world: 'MAIN', }, ]);
In the example above, in-page.js
is injected and executed within the main content tab every time a new page is loaded. This in-page.js
file sets window.ethereum
for all dApps to use. If the world
is undefined
or isolated
, the script would still execute but would do so in an isolated environment.
Manifest version 3 work is quite the slog so please hug your closest extension developer. There are many huge structural changes and navigating those changes is a brutal push!
CSS @supports
Feature detection via JavaScript is a client side best practice and for all the right reasons, but unfortunately that same functionality hasn’t been available within CSS. What we end up doing is repeating the same properties multiple times with each browser prefix. Yuck. Another thing we…
dat.gui: Exceptional JavaScript Interface Controller
We all love trusted JavaScript frameworks like MooTools, jQuery, and Dojo, but there’s a big push toward using focused micro-frameworks for smaller purposes. Of course, there are positives and negatives to using them. Positives include smaller JS footprint (especially good for mobile) and less cruft, negatives…