UBS React Js Software Engineer Interview Questions and Answers

Explaining the features and usage of ReactJS

• Strict mode catches common mistakes and enforces best practices

• ForwardRef allows passing refs to child components

• Keys help React identify which items have changed, added, or removed

• Controlled components are stateful and rely on props to update, while uncontrolled components manage their own state

• Accessibility in React involves using ARIA attributes and semantic HTML

ES6 features, shallow and deep cloning, hoisting, JS execution cycle.

• ES6 features include arrow functions, template literals, let and const, destructuring, spread and rest operators, etc.

• Shallow cloning creates a new object with the same properties as the original object. Deep cloning creates a new object with all nested objects also cloned.

• To deep clone nested objects, use a recursive function or a library like lodash...read more

Hooks can be tested using React Testing Library or Enzyme.

• Use React Testing Library's renderHook() method to test hooks

• Test the hook's return value and its behavior on re-renders

• Use Enzyme's shallow() or mount() methods to test hooks

• Mock any external dependencies used in the hook

• Test edge cases and error handling