Frontend Screening Interview Questions

josys-frontend-interview-screening-questions.md

Frontend Screening Interview Questions

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Q. How do you check if a variable holds an array?

A. Using Array.isArray function.

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Q. How would you generate a long string of a single character?

A. Using String.repeat function. Example, 'M'.repeat(255); will generate 255 M characters in a single string

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Q. Is Promise constructor async like setTimeout or sync?

A. It is sync.

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Q. What is the difference between Function.call and Function.bind?

A. Function.bind returns a new function with bounded arguments, while Function.call just calls the function with the given arguments.

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Q. What is the difference between Function.reduce and Function.map?

A. Function.reduce acts like a collection aggregator while Function.map just returns a new array probably after performing some calculation on the original array's elements.

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Q. When would you opt for using Map instead of a simple object?

A. If we have constantly changing object then we would use Map for its high performance, while for static objects a simple object would work.

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Q.When do useMemo and useEffect run in a component life cycle?

A. useMemo runs before a component renders while useEffect runs after component has rendered and is mounted in the browser DOM.

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Q. Would you choose React Context to store the application data or a state manager?

A. Use a state manager always, Context is used only for light weighted information sharing.

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Q. What are the advantages of CSS-in-JS and CSS Modules over the standard CSS in React?

A. These solutions scope the CSS thus a developer is free to use same CSS rule name across the project without having a name collision and rules overriding.