A component changes its state by calling the function

A component changes its state by calling the function

• A. this.setState( { someKey: newValue} );
• B. this.updateState( { someKey: newValue} );
• C. this.changeState( { someKey: newValue} );
• D. setState( { someKey: newValue} );

Answer: (A)

In React class components, updating state is done with this.setState. This method is the built-in way to queue a state change and trigger a re-render. Passing an object like { someKey: newValue } tells React to merge that partial state into the current state, leaving the rest untouched. That merge-and-render behavior is what makes this approach correct for changing the component’s state. The other options aren’t part of React’s standard class component API for updating state. They would either refer to custom methods you’d have to define yourself, or in the case of a plain setState without this, point to something outside the component’s instance, which wouldn’t update the component’s state or cause a re-render.

In React class components, updating state is done with this.setState. This method is the built-in way to queue a state change and trigger a re-render. Passing an object like { someKey: newValue } tells React to merge that partial state into the current state, leaving the rest untouched. That merge-and-render behavior is what makes this approach correct for changing the component’s state.

The other options aren’t part of React’s standard class component API for updating state. They would either refer to custom methods you’d have to define yourself, or in the case of a plain setState without this, point to something outside the component’s instance, which wouldn’t update the component’s state or cause a re-render.