fix(userId): Prevent the id from resetting on every page refresh

[duailibe]

The getUserId() function, when run for the first time, tries to fetch the user id from a cookie, but the current regex is not getting it correctly. This causes the user id to be reset every time the library loads

[duailibe]

Added a failing test here so you can see the problem happening.

The fix should be as simple as removing the forward slash / from the beginning and the end of the regex

analytics.js/src/detector.ts

Line 58 in 6ca0c5c

const regex = new RegExp("/(^|;)\\s*" + cookieName + "\\s*=\\s*([^;]+)/");

Since it's using the RegExp() constructor, those are escaped and will never match anything in document.cookie

[sk-]

Thanks @duailibe for the PR and the report of the issue. The test you added correctly shows the issue you mentioned.

Would you be adding the fix you proposed in #182 (comment) ?

[duailibe]

@sk- Pushed a commit with a fix. Let me know if there's anything else you need me to do

Thank you!

[sk-]

Thanks @duailibe, we will be releasing a new version including these changes soon.