Where is the initial state typically assigned in a class-based component?

Where is the initial state typically assigned in a class-based component?

• A. In the class body outside of any method
• B. In componentDidMount
• C. In the constructor using this.state
• D. In the render method

Answer: (C)

Initial state in a class-based React component is set in the constructor using this.state. The constructor runs before the component is mounted, so it’s the right place to establish the starting state value that the first render will use. You typically write something like: constructor(props) { super(props); this.state = { /* initial fields */ }; }. This pattern guarantees that render has a state object to read from on the initial pass. Don’t try to set or mutate state inside render, because render should be pure and only reflect the current state. componentDidMount runs after the first render, so it’s for side effects, not for initializing state. While modern syntax can initialize state as a class field, the traditional and most common approach is inside the constructor using this.state.

Initial state in a class-based React component is set in the constructor using this.state. The constructor runs before the component is mounted, so it’s the right place to establish the starting state value that the first render will use. You typically write something like: constructor(props) { super(props); this.state = { /* initial fields */ }; }. This pattern guarantees that render has a state object to read from on the initial pass. Don’t try to set or mutate state inside render, because render should be pure and only reflect the current state. componentDidMount runs after the first render, so it’s for side effects, not for initializing state. While modern syntax can initialize state as a class field, the traditional and most common approach is inside the constructor using this.state.