If you're a web developer, JavaScript is probably the language you're using the most. But it's also a language that never ceases to gives us surprises. How many times did we say "Huh, so it behaves like that!", or "I didn't know that API existed!", or just "This is so weird..."
And it's just that: JavaScript is weird. Being the language itself, with its quirkiness thoroughly examined in many occasions; or in the case of weird, less-known, or just DOM APIs with unusual signatures and implementations. But maybe some of these techniques, which could have been common knowledge, are still useful today and could solve our day-to-day problems.
Just don't use them in production! Not for now, at least...