Frontend

What does it mean that props did not change in the context of React.memo?

Implement a map function for an iterator that transforms its values, for example by multiplying each random number by 2.

Middle

МТС Digital

Do you have experience testing frontend?

What is the difference between interface and type in TypeScript? How to combine two interfaces into one?

Why does the "Similar Products" block start to work incorrectly when quickly switching between different product pages? Find and fix the problem.

What does throw new Error(...) do in a Promise chain, and how is it different from return new Error(...)?

Implement toggle of square state on click: on first click, the square becomes green; on second click, it reverts to red.

What happens under the hood of Redux Toolkit when the state changes?

Do you have experience using View and Materialized View in PostgreSQL?

What is the time complexity of quicksort?

Middle+

СБЕР

What are prototypes and prototypal inheritance in JavaScript?

Write a generic function/type that can handle user data, and explain how to constrain the generic.

How often does the ref trigger on changes?

What is hydration in React/Next.js and what happens during hydration mismatch?

Why do results not reset after clearing the search string completely? Find and fix the reason in debounce logic.

Do you have tight deadlines and how actively are you currently interviewing?

What utility types in TypeScript do you know? What is the difference between any and unknown?

In what order will the values be output?

There are three nested elements: form, div, and p, each with a click event handler. What will happen when clicking on the div element?

What is a CORS preflight request and in which cases does the browser send it? When can a request be sent without preflight?