Prepare expansion of public JavaScript API of GOV.UK Frontend

[romaricpascal]

Brief

Design public JavaScript features to be provided by GOV.UK Frontend, both for interacting with components (methods, events, callbacks) and for building components that do not exist in GOV.UK Frontend.

Plan the documentation of such features in the Frontend docs site.

As a stretch, start strenghtening components initialisation so that:

• components error if initialised twice on the same element
• existing component instances can be obtained for a given component

Epic lead

Romaric

Driving role(s)

Developers, Technical writer

Supporting roles

N/A

Needs awareness

N/A

Further detail

Design a public API

Beta Give feedback

1. Review ports for possible hints at what our API could do #5148
   javascript 🔍 investigation +2
   
2. Gather what our components do with their internal API #5149
   javascript 🔍 investigation +2
   
3. Review usage of our components across teams at GDS #5151
   javascript 🔍 investigation +2
   
4. Ask community feedback on which features they'd find useful during Monthly chat #5152
   event +1
5. Review feedback from Monthly chat #5173
   javascript +1
6. Create speculative APIs for each components #5147
   javascript 🔍 investigation +2
7. Agree on conventions across components #5174
   javascript +1

Prepare API documentation

Beta Give feedback

1. Catch up with Pay to discuss how they do their API documentation #5153
   documentation javascript +2
2. Collect examples of good JavaScript API documentations #5155
   documentation javascript +2
3. Spike how we can integrate information from Typedoc in our own docs #5157
   documentation javascript +2

[romaricpascal]

Closing this one as we're carrying on a more focused piece of work in #5205 and can pick up the remaining open issues when needs arise.