Building a tooltip? A carousel? A password input? I can strongly recommend checking if the Component Gallery has a page on whatever UI pattern you're working on.

Each entry collates examples from design systems and pattern libraries all over the web, so you can quickly compare how everyone from Google and Salesforce to Brighton & Hove City Council have solved your problem.

It's been invaluable for the design system project I've been working on, as much for uncovering best practices as simply dissecting the sometimes opaque terminology that has evolved around certain UI patterns.