Senior React interview questions

What we will cover

• Interview questions that I would ask a mid to senior level React developer

Notes

Before we start it is important to note that interview questions for juniors and seniors have a different goal.

In the junior case we are interested in figuring out if there is a potential in the candidate to become productive and in the senior case we are looking for experience.

The following questions are aimed to figure out how much experience a candidate has and if they know what it means to work on big projects.

Questions

• What tools suite do you use for your project and why?

  • Bad: "Parcel, NextJS and JS++"
  • Good: "Webpack, React router and TypeScript"

• What testing strategy do you use?

  • Bad: "I mostly do manual testing/TDD"
  • Good: "I use TDD for logic and automated UI tests for the rest"

• How do you handle component reuse?

  • Bad: "I always try to write generic components"
  • Good: "I refactor when I see duplication but some components are generic"

• When do you use server side rendering and why?

  • Bad: "I always use it because it speeds up the loading time"
  • Good: "I haven't used it because I don't work in Node"

• What tasks do you run and how?

  • Bad: "I mostly use Webpack loaders"
  • Good: "I try to use a task runner and Webpack for bundling"

• When do you use component based testing and why?

  • Bad: "I use Enzyme and I try to test all my components"
  • Good: "I use Enzyme but only for generic components since I use UI testing mostly"

• Do you use TDD and how?

  • Bad: "I use TDD as much as I can"
  • Good: "I find it hard to use TDD for components so I use it for logic"

• What state do you put where and why?

  • Bad: "I always put my state on the store"
  • Good: "I only put shared data on the store and private data on the state"

• Whats more important, clean code or good enough?

  • Bad: "Clean code"
  • Good: "I try to write clean code but sometimes I need to hack things together"

The following questions will indicate how big the projects the candidate has been involved in are

• How do you handle bundling performance?

  • Bad: "What do you mean?"
  • Good: "There are loaders for it but mostly I try to reduce the bundling process"

• How do you handle multiple component variants in the same codebase?

  • Bad: "I try to refactor them in to generic components"
  • Good: "I raise awareness in the company and take action after that"

• How do you handle feature toggling?

  • Bad: "What do you mean?"
  • Good: "I use a config file or similar"

• How do you avoid component duplication?

  • Bad: "I write generic components and put them in Storybook"
  • Good: "It is hard to solve this so I talk to the teams and use good names"

• How do you handle A/B testing?

  • Bad: "What do you mean?"
  • Good: "I create a temporary component in isolation"

• How do you handle branding/themes?

  • Bad: "I use Material ui themes"
  • Good: "I try to avoid them / I use a variant prop in the components"

• How do you handle translations?

  • Bad: "I have never worked with them / we use translation files"
  • Good: "We get them from a external tool"