React Components and JSX Interview Questions With Answers
Components and JSX are core interview territory. Here are the questions that come up and how to answer them with understanding.
React Components and JSX Interview Questions With Answers
Interviewers probe components and JSX because they reveal whether you understand React's fundamentals. Here are the questions that come up and how to answer them well.
What is a React component?
A component is a reusable, independent piece of UI described as a function that returns JSX. It accepts props and manages its own state, and React composes components to build full UIs.
What is the difference between props and state?
Props are inputs passed from a parent to a child and are read-only inside the child. State is internal data managed by the component that can change and trigger re-renders.
What is JSX?
JSX is a syntax extension for JavaScript that compiles to React.createElement calls. It lets you write UI descriptions in a markup-like style while remaining pure JavaScript.
Why must component names be capitalized?
React treats lowercase tag names as DOM elements and capitalized names as components. Capitalization is how React distinguishes a custom component from an HTML tag.
What is the difference between controlled and uncontrolled components?
Controlled components have their value controlled by React state. Uncontrolled components keep their state in the DOM, accessed via refs. Controlled is the React-preferred pattern.
How to Answer Well
Give the definition, then the reasoning. Interviewers want to see you understand why, not just what. Explain props vs state with a concrete example, and JSX with the compilation story.
The Takeaway
Components and JSX questions test fundamentals. Know what a component is, props vs state, what JSX compiles to, why names are capitalized, and controlled vs uncontrolled. Answer with reasoning, not just definitions.
A component is a reusable, independent piece of UI described as a function that returns JSX. It accepts props, can manage its own state, and React composes many components to build full user interfaces.
Props are inputs passed from a parent to a child and are read-only inside the child. State is internal data managed by the component that can change over time and trigger re-renders.
JSX is a syntax extension for JavaScript that compiles to React.createElement calls. It lets you write UI descriptions in a markup-like style while remaining pure JavaScript that can embed expressions.
React treats lowercase tag names as DOM elements like div and capitalized names as components. Capitalization is how React distinguishes a custom component from a built-in HTML tag.
Controlled components have their value controlled by React state via props. Uncontrolled components keep their state in the DOM, accessed via refs. Controlled is the React-preferred pattern for forms.
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