componentDidMount() { const incFunc = () => this.setState( {counter: this.state.counter + 1}); this.timerID = setInterval(incFunc, 2 * 1000); } calender code example

Example: setstate react js

constructor(props) {
        super(props);
        this.state = {
            isActive: true,
        };
    }

    checkStatus = () => {
        this.setState({		// use this function
            'isActive' : !this.state.isActive,
        });
    }