Implement newer techniques made available by our support strategy

[romaricpascal]

What

We're updating our components to use actual classes rather than functions with a prototype.

Internally, we're also updating our tools and linting configuration now they're no longer held back by the need to support old browsers.

Why

Besides their more compact syntax, using classes will open the door to factorising common component behaviours so it can be inherited by the different components sharing them.

Updating our tools will allow us to benefit from their latest features, and our linting will need to match the newer features we're now able to use.

Who needs to work on this

Developers

Who needs to review this

Developers

Tasks

v5

Preview Give feedback

1. Upgrade Rollup #3462
   javascript tooling +2
2. Upgrade ESLint configuration #3463
   javascript tooling +2
3. Migrate JavaScript to ES2015 classes #3506
   11 of 11
   javascript +1
4. Unpin autoprefix and update it to the latest version (See Upgrade to Autoprefixer v10 #3243)

Post v5

Preview Give feedback

1. Document conventions on techniques we're OK to use or not (destructuring, new syntaxes...)