A recruiter approached me through email. I had a quick online interview with typical HR questions (experience, why would you like to join, etc) and 4 very simple technical questions. The interviewer was very polite and explained the entire process. Afterwards, I received a coding challenge via email and was given 3 weeks to complete it. The interviewer garanteed I could take my time. I completed it in something like 10 hours over the span of 1 week and a half (busy week at work) and delivered the results pretty confident that I wrote clean code, with tooling, comments and even specs. After that, in half a day I received a single "no" with zero feedback. I suspect they are not measuring your ability to solve the problem, but something else, as it was pretty much solved perfectly... Anyways, I was saddened by the lack of feedback - as others pointed out, if we gave them hours of time, they could at least point what was missing.

Very nice interviewer. Very casual. No BS intro and talking points. Actually, read the CV before the interview. The interview was as scheduled for 45 minutes. 2 questions, knowledge of javascript internals and DOM manipulation.