Which statement about event handlers in class components is true?

Which statement about event handlers in class components is true?

• A. They are defined as methods on the component class
• B. They must be bound in the constructor only
• C. They cannot be used in class components
• D. They are defined as separate functions outside the class

Answer: (A)

Event handlers in class components are defined as methods on the component class. This setup lets the handler access the component’s instance data, like this.state and this.props, and call methods to update state in response to user interactions. You typically declare a method inside the class, such as handleClick() { … }, and attach it in render with onClick={this.handleClick}. Since the function needs the correct this binding, you bind it to the component instance—either in the constructor (this.handleClick = this.handleClick.bind(this);) or by using the class field syntax (handleClick = (e) => { … }), which auto-binds. Defining handlers outside the class or binding only in the constructor aren’t the sole or required approaches, and event handlers can and do work inside class components.

Event handlers in class components are defined as methods on the component class. This setup lets the handler access the component’s instance data, like this.state and this.props, and call methods to update state in response to user interactions. You typically declare a method inside the class, such as handleClick() { … }, and attach it in render with onClick={this.handleClick}. Since the function needs the correct this binding, you bind it to the component instance—either in the constructor (this.handleClick = this.handleClick.bind(this);) or by using the class field syntax (handleClick = (e) => { … }), which auto-binds. Defining handlers outside the class or binding only in the constructor aren’t the sole or required approaches, and event handlers can and do work inside class components.