Senior Front End Engineer Interview Questions

2,000 senior front end engineer interview questions shared by candidates

Serialise IDs from a nested tree of items
 const data = [
  { id: 1, items: [{ id: 4, items: [{id: 5}, {id: 6, items: [{id: 8}]}]}]},
  { id: 2, items: [{ id: 7}]},
  { id: 3 },
  { id: 9, items: [{id: 10, items: [{id: 12}]}, {id: 11}] }
];

// Should return [1, 2, 3, 9, 4, 7, 10, 11, 5, 6, 12, 8] 
avatar

Senior Front End Developer

Interviewed at Apple

4.1
Nov 10, 2017

Serialise IDs from a nested tree of items
 const data = [
  { id: 1, items: [{ id: 4, items: [{id: 5}, {id: 6, items: [{id: 8}]}]}]},
  { id: 2, items: [{ id: 7}]},
  { id: 3 },
  { id: 9, items: [{id: 10, items: [{id: 12}]}, {id: 11}] }
];

// Should return [1, 2, 3, 9, 4, 7, 10, 11, 5, 6, 12, 8] 

They asked me to explain how I would approach optimizing the performance of a web application. It was a great question because it allowed me to demonstrate my practical experience, talk about specific tools and techniques I use, and show how I think through real-world challenges.
avatar

Senior Front End Developer

Interviewed at EPAM Systems

4
Apr 18, 2025

They asked me to explain how I would approach optimizing the performance of a web application. It was a great question because it allowed me to demonstrate my practical experience, talk about specific tools and techniques I use, and show how I think through real-world challenges.

Really basic questions about typescript and HTML at beginner level.: What do you think about using "any" as a type... Do you put all your css in one file? What is the difference between var and let... + many other junior level questions.
avatar

Senior Front End Developer

Interviewed at PlayStation

4.1
Dec 19, 2022

Really basic questions about typescript and HTML at beginner level.: What do you think about using "any" as a type... Do you put all your css in one file? What is the difference between var and let... + many other junior level questions.

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