Amend explicit-cross-domain-links.js code

[danacotoran]

Amend explicit-cross-domain-links code to account for the possibility of someone accepting/rejecting cookies on the page that the cross-domain link is present.

This was raised as a bug on the Brexit page, where the Sign in link is a cross-domain link (leading to DI Sign In territory).
If someone has interacted with the cookie banner on this page, the link treats them as if they have not, i.e the ?cookie_consent=not_engaged parameter remains unchanged, and the GA parameter is not added (if they have accepted cookies). The setting applies only after the page is reloaded.

Before (the correct parameters are appended to the cross domain link only after the page is reloaded)

Screen.Recording.2021-11-23.at.11.37.33.mov

After (the correct parameters are appended to the cross domain link instantly when cookies are accepted or rejected)

Screen.Recording.2021-11-23.at.13.30.20.mov

Upon detecting the cookie consent or rejection event, the cross-domain link module should re-run and append the correct parameters to any cross domain links present on the page.

[andysellick]

Overall looks good, one minor comment.

The code for explicit-cross-domain-links was already a bit of a spaghetti before these changes, I think once this change has gone in we should look at refactoring the code a little bit to make it clearer. Specifically there are a lot of guard clauses in the start function that maybe could be consolidated, and the whole thing could be restructured to make it more understandable. Something like:

window.addEventListener('cookie-consent', this.cookiesAreAccepted)
window.addEventListener('cookie-reject', this.cookiesAreRejected)

...

this.cookiesAreNotAnything = function () {
  this.decorate(element, 'cookie_consent=not-engaged')
}

this.cookiesAreAccepted = function () {
  // something here
}

this.cookiesAreRejected = function () {
  this.decorate(element, 'cookie_consent=reject')
}

[andysellick]

These three lines appear to be duplicated in the previous test - could they be moved into a beforeEach function for this describe block?

[danacotoran]

Great point, have updated as suggested.