You can't call this.setState() from inside of which part of the component lifecycle?

You can't call this.setState() from inside of which part of the component lifecycle?

• A. render function
• B. the render function
• C. constructor
• D. componentDidMount

Answer: (B)

The main idea here is that render must be a pure function. It should read the current props and state and return the UI without causing side effects. Calling this.setState inside the render method would schedule another update while React is in the middle of rendering, which would trigger another render, and so on. That creates an infinite loop and a broken UI. So, the render method is the place you should not call setState. You initialize state in the constructor by assigning to this.state, and you can update state later in lifecycle methods like componentDidMount or componentDidUpdate when appropriate (for example, after data fetch).

The main idea here is that render must be a pure function. It should read the current props and state and return the UI without causing side effects. Calling this.setState inside the render method would schedule another update while React is in the middle of rendering, which would trigger another render, and so on. That creates an infinite loop and a broken UI.

So, the render method is the place you should not call setState. You initialize state in the constructor by assigning to this.state, and you can update state later in lifecycle methods like componentDidMount or componentDidUpdate when appropriate (for example, after data fetch).