Fidelis Technology Services Senior Software Engineer Interview Questions and Answers for Experienced

React lifecycle, Fragment vs React.Fragment, React.PureComponent

• React lifecycle consists of mounting, updating, and unmounting phases

• Fragment is a shorthand for React.Fragment, used to group multiple elements

• React.PureComponent is a class component that implements shouldComponentUpdate method for performance optimization

JavaScript hoisting and differences between let, var and const.

• Hoisting is a JavaScript mechanism where variables and function declarations are moved to the top of their scope.

• Var declarations are hoisted to the top of their scope, while let and const declarations are not.

• Var can be redeclared and reassigned, let can be reassigned but not redeclared, and const cannot be reassigned or redeclared.

• Using const is recommend...read more

Prevent rerendering of a child component in React

• Use shouldComponentUpdate() lifecycle method

• Use React.memo() to memoize functional components

• Use PureComponent instead of Component

• Pass props as a callback function to avoid unnecessary re-renders

• Use React.PureComponent for class components

• Use React.memo() for functional components