Incrementing state value by one using React

Question

In React I am trying to make a button increment a value stored in state. However using the code below function my value is set undefined or NaN when using handleClick.

Answer 1

class SkuVariantList extends React.Component {
    constructor(props) {
      super(props)
      this.state = {
        clicks: 0
      };
      this.clickHandler = this.clickHandler.bind(this)
    }

    componentDidMount() {
      this.refs.myComponentDiv.addEventListener('click', this.clickHandler);
    }

    componentWillUnmount() {
      //this.refs.myComponentDiv.removeEventListener('click', this.clickHandler);
    }

    clickHandler() {
      var clk = this.state.clicks
      this.setState({
        clicks: clk + 1
      });
    }

    render() {
      let children = this.props.children;

      return (
        

          
My Component ({this.state.clicks} clicks})
          
{this.props.headerText}
          {children}
        
      );
    }
  }