Uncaught TypeError: Cannot read property 'state' of undefined - React

Question

I can not figure out if I am missing something small here?

Just trying to get a grasp on how state works with React.

Just creating a small check box that change

Answer 1

Binding your handleCheck function in the constructor:

constructor(props) {
    super(props);

    this.state = {
        checked: true
    };

    this.handleCheck = this.handleCheck.bind(this);
}