To note a few things regarding the interview and hiring process (I do a lot of it, have done about 20 in the past two days), the reason for the quiz and not using your portfolio (unless its extremely outstanding and you are fine doing a live coding questionnaire) is so that we can judge all the candidates equally and fairly.
It gives a common baseline to judge. Each candidate does the same thing and we have a good idea of what we are looking for, the rest of it tells us how you think, how you approach your work, organize your work, and best of all? You can compare that to how others do it.
Now, not to say that's everyone, that is what we use it for.
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Before, as an Engineer / Manager, I hated doing "live coding" tests when it wasn't relevant. For example doing "algorithms" or "palindrome" or "sliding window dns" or "O(n)" examples when you're doing front-end or a management position screams to me that the people doing the interviewing don't know what they actually want.
Instead quizzes or live coding that are relevant like "tell me how to access all the elements in this particular element and traverse the children to apply some styling" is much more relevant and will show me the thought process, their ability to retain information, and their recall. It also shows communication ability when they get stuck and ask for help or use me as a sounding board.
It's not always about your implementation, but how you handle the situation and communicate