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Yup. I’m hiring for a mid-level FE role right now, and the number of “React developers” that don’t know JS fundamentals is incomprehensible. I’m not talking abo

Yup. I’m hiring for a mid-level FE role right now, and the number of “React developers” that don’t know JS fundamentals is incomprehensible. I’m not talking about anything esoteric. Just the sorts of things that I as someone that’s far from a JS expert considers necessary to work in that space day to day. I’m more and more just taking it as a given now that someone won’t have much if any experience writing CSS by hand. If they do, never in an actual .css file. Always via some CSS in JS something or other. A strange new world out there.

ssijak 3y ago
Give us some examples of JS fundamentals they do not know
- jahewson 3y ago
  Not op but “write hello world to the DOM” and “make an http request” are questions I’ve seen go unanswered many times.
  - pronik 3y ago
    "make an http request" as in fetch() would be OK, but doing "classic" XHR in an interview? Hell no, I've got better things to do.
  - Gigachad 3y ago
    Honestly I can’t remember half the dom manipulation stuff and at one point I did know it quite well. It’s just been 6 years since I worked on an app that wasn’t react. It’s useless knowledge for most people now. Like knowing assembly.
    - pcthrowaway 3y ago
      I wouldn't really consider anything involving the DOM to be a JS fundamental. That's a browser fundamental, and even then, it's like, what do you want? I can use `document.write('hello world')` and replace the entire body. Or append it as a text node with `document.body.append`. Or create an element and add it. This is a pretty silly question and something people should just spend 2 seconds looking up on the rare occasion they need to do it. I currently work with devs who've done things like create a Map and then assign properties directly instead of using .set and .get.. I'd say that shows a pretty significant lack of fundamentals
      - brandensilva 3y ago
        I believe Map was released in 2015 as part of ES6 so while not new, it still feels new in some code bases. Some people also confuse it with Array.prototype.map a lot. People just assume every data structure operates like an array since it is the most commonly used without realizing the underlying object nature of the language. Like the idea of getters and setters coming from OOP paradigm is lost to fresh devs over the last 5 years using the FP paradigm as their primary means of coding in React. So yeah some of the fundamental are missing but also most of the time this knowledge probably isn't utilized by React FP only devs in their day to day.
- technion 3y ago
  I write this blog a while ago: https://lolware.net/blog/react-xss-protection-cheat-sheet/ https://lolware.net/blog/react-xss-protection-cheat-sheet/ The feedback I got across the board was generally "what even is this code? If you it to work with react why isn't it a hook?"
  - moritzwarhier 3y ago
    What does "across the board" mean? You mention that the article scores for newbie Google searches about XSS in React. I mean, it's correct that people who ask such questions should spend a year doing web dev without React probably (and maybe learn basic programming concepts). But the people who comment to you about that post seem to be self-selected for not knowing much about JS. People who know their ropes aren't left with any questions by your article :) and probably know about everything it contains already. Still, feedback from me: good content, especially for beginners!
- 65 3y ago
  I would assume array methods (map, filter, reduce), callbacks, hoisting, mutability, etc. I've interviewed a few people who don't know how some of the array methods work, and those are one of the most important parts of knowing how to write Javascript.
Tade0 3y ago
I've reduced my JS interview test to just one question: "What examples of falsy values can you name?". Anyone working with the language will be inevitably regularly reminded which these are. The least mentioned is NaN followed up by... false. But I can't blame anyone for forgetting that one, as it's too obvious.
- mvdtnz 3y ago
  That's one of the worst interview questions I have ever heard.
  - intothemild 3y ago
    If its just the one question then sure i agree... but if it was used as a kind of fun icebreaker question, then I can kind of see where it could be used. But it's just very much asking around https://javascriptwtf.com/ https://javascriptwtf.com/ level stuff
    - Tade0 3y ago
      Can't agree here. Especially when you deal with unsanitized data - like from a 3rd party API - you're bound to eventually have each of those cases find their way into your if statements/expressions. Also, this question works for other languages too, as e.g. NaN can evaluate to True (Python) or have an undefined behaviour but still evaluate to true (C, C++) - it's useful to know what is true and what is false(y) in your language of choice, especially coming from another language.
  - Tade0 3y ago
    Thank you for your opinion - it's proven reliable over the last decade.
  - rvba 3y ago
    Since I didnt think such word even exists I googled and apparently there is something called "falsy" in javascript. To make it worse, there is a "truthy" too. I guess a technical question. But my eyes.

ssijak 3y ago

Give us some examples of JS fundamentals they do not know

jahewson 3y ago
Not op but “write hello world to the DOM” and “make an http request” are questions I’ve seen go unanswered many times.
- pronik 3y ago
  "make an http request" as in fetch() would be OK, but doing "classic" XHR in an interview? Hell no, I've got better things to do.
- Gigachad 3y ago
  Honestly I can’t remember half the dom manipulation stuff and at one point I did know it quite well. It’s just been 6 years since I worked on an app that wasn’t react. It’s useless knowledge for most people now. Like knowing assembly.
  - pcthrowaway 3y ago
    I wouldn't really consider anything involving the DOM to be a JS fundamental. That's a browser fundamental, and even then, it's like, what do you want? I can use `document.write('hello world')` and replace the entire body. Or append it as a text node with `document.body.append`. Or create an element and add it. This is a pretty silly question and something people should just spend 2 seconds looking up on the rare occasion they need to do it. I currently work with devs who've done things like create a Map and then assign properties directly instead of using .set and .get.. I'd say that shows a pretty significant lack of fundamentals
    - brandensilva 3y ago
      I believe Map was released in 2015 as part of ES6 so while not new, it still feels new in some code bases. Some people also confuse it with Array.prototype.map a lot. People just assume every data structure operates like an array since it is the most commonly used without realizing the underlying object nature of the language. Like the idea of getters and setters coming from OOP paradigm is lost to fresh devs over the last 5 years using the FP paradigm as their primary means of coding in React. So yeah some of the fundamental are missing but also most of the time this knowledge probably isn't utilized by React FP only devs in their day to day.
technion 3y ago
I write this blog a while ago: https://lolware.net/blog/react-xss-protection-cheat-sheet/ https://lolware.net/blog/react-xss-protection-cheat-sheet/ The feedback I got across the board was generally "what even is this code? If you it to work with react why isn't it a hook?"
- moritzwarhier 3y ago
  What does "across the board" mean? You mention that the article scores for newbie Google searches about XSS in React. I mean, it's correct that people who ask such questions should spend a year doing web dev without React probably (and maybe learn basic programming concepts). But the people who comment to you about that post seem to be self-selected for not knowing much about JS. People who know their ropes aren't left with any questions by your article :) and probably know about everything it contains already. Still, feedback from me: good content, especially for beginners!
65 3y ago
I would assume array methods (map, filter, reduce), callbacks, hoisting, mutability, etc. I've interviewed a few people who don't know how some of the array methods work, and those are one of the most important parts of knowing how to write Javascript.

Tade0 3y ago

I've reduced my JS interview test to just one question: "What examples of falsy values can you name?". Anyone working with the language will be inevitably regularly reminded which these are. The least mentioned is NaN followed up by... false. But I can't blame anyone for forgetting that one, as it's too obvious.

mvdtnz 3y ago
That's one of the worst interview questions I have ever heard.
- intothemild 3y ago
  If its just the one question then sure i agree... but if it was used as a kind of fun icebreaker question, then I can kind of see where it could be used. But it's just very much asking around https://javascriptwtf.com/ https://javascriptwtf.com/ level stuff
  - Tade0 3y ago
    Can't agree here. Especially when you deal with unsanitized data - like from a 3rd party API - you're bound to eventually have each of those cases find their way into your if statements/expressions. Also, this question works for other languages too, as e.g. NaN can evaluate to True (Python) or have an undefined behaviour but still evaluate to true (C, C++) - it's useful to know what is true and what is false(y) in your language of choice, especially coming from another language.
- Tade0 3y ago
  Thank you for your opinion - it's proven reliable over the last decade.
- rvba 3y ago
  Since I didnt think such word even exists I googled and apparently there is something called "falsy" in javascript. To make it worse, there is a "truthy" too. I guess a technical question. But my eyes.