Reactjs component `this.state` undefined

Question

I'm new to reactjs and tried to make a component. I set this.state in componentWillMount() and after that I call a method:

componentWillMount() {
        this.setState({ value: this.props.value || "0" });
        this.changeCbState = this.changeCbState.bind(this); 
        this.changeCbState();
    }

But in my method changeCBState this.state is undefined:

changeCbState() {
        console.log(this.state.value)
    }

Error: Uncaught TypeError: Cannot read property 'value' of null

Answer 1

The problem could be that you wouldn't have initialised state in the constructor and since this.setState is asynchronous the state may not be initialsed before you are trying to access in changeCbState function.

Also the initialisation code that you have written in componentWillMount lifecycle needs to go in constructor since the componentWillMount method is supposed to be deprecated.

constructor(props) {
    super(props);
        this.state = {
           value: this.props.value || "0"
        }
        this.changeCbState = this.changeCbState.bind(this); 
        this.changeCbState();
    }