componentDidMount() {
        // fade away over 2 seconds, after 4 seconds, then self delete
        let counter = 0
        const fadeAt = 4000
        const fadeTime = 2000
        const interval = 100
        this.intervalId = setInterval(() => {
            counter += interval
            if (counter >= fadeAt + fadeTime) {
                // done fading
                this.props.onDeleted(this.props.id)
            }

            if (counter > fadeAt) {
                const fadeTimeElapsed = counter - fadeAt
                this.setState({ opacity: Math.round((fadeTimeElapsed / fadeTime) * 100)})
            }
        }, interval)
    }

    componentWillUnmount() {
        clearInterval(intervalId)
    }