This article should interest you if you’re starting to interview people (since these are relatively standard questions), or if you’re a junior developer preparing for interviews.
Focus on commonly used APIs
As an easy question, I ask to cite some functions of the prototype of Array (some, reduce, map, etc.) and how they work, features of ES2015/2016 (I often also ask if an object assigned with a const is mutable and the difference between an arrow function and a normal one (hint, it’s the this)).
I have several “harder” questions, and most of them are related to “how the language work”, rather than “what is this obscure JS API”. There are so many ways to write JS, so many libraries, and so many APIs, that I don’t think that knowing them (or not) is important. There was a thread on Twitter a bit ago of famous senior developers telling what were the basic APIs that they would google everyday when coding. For me, it’s slice and splice. I cannot remember the difference, and how they arguments work. But does it really matter? I can check it in thirty seconds.
I also used to ask for languages quirks, but I’m less and less convinced it’s important (e.g.
0.1 + 0.1 + 0.1 !== 0.3 ,
typeof null === 'object' ). No strong feeling about that.
How JS and the DOM work
If you think I’m missing something, or if you know other questions, I’m all ear! You can also reach me on twitter.