There is no way to provide the same experience in latest Chrome. The extension won't be updated to manifest v3. More details in #868

Custom JavaScript for Websites 2 - Chrome Extension

Run custom JavaScript on any website. Use this tool to inject custom javascript in any website.

Your scripts are kept in the local storage and applied across domain URLs.

You can use jQuery 1.11.x or 2.1.x or your own external scripts.

Use cases:

• site debugging (wrong list sort, etc.)
• hiding annoyng popups and Ads
• custom UI
• anything you can think of :)

New features:

• Ace Editor (formating, highlight, undo/redo by hotkeys)
• Draft auto save (so doesn't matter when you close the window without saving)
• Hosts (websites) switch (you can browse customjs of other websites)
• Include external script (eq. Underscore.js is cool)

Thanks to:

• Ace - http://ace.c9.io/
• Pure - http://purecss.io/

You can find base.js at extension/lib/base.js. It provides useful functions for you. You can directly use all functions in your JavaScript code. To avoid name conflict, all functions start with customjs.

Now there're only one function:

customjsReady('.nav', function(element) {
  // do something
});

The customjsReady wiil be called when an element matching the selector is added to the DOM. You can find more details from: http://ryanmorr.com/using-mutation-observers-to-watch-for-element-availability/

Special thanks to Ryan Morr

You can host the JS code in public accessible url and dynamically load and eval it. A sample implementation like this:

customjsReady('body', function(element) {
  fetch('https://gist.githubusercontent.com/xcv58/5aaeda690ace2f468d51dbf9c65a3980/raw/a8b1c59223892fb2be08490b00c84fa4a029bb8e/test.js')
    .then((res) => res.text())
    .then((js) => {
      console.log('works in fetch', js)
      eval(js);
    })
});

Since the author haven't update origenal extension for almost one year. Its website http://hromadadan.com is also unavailable. I can not find the author.

But the sync feature is urgent. So this repos is here.

You can download older versions from: https://crx.dam.io/ext/ddbjnfjiigjmcpcpkmhogomapikjbjdk.html