LazyLoading-CodeSample-1.js

componentDidMount() {
    this.detectInViewport()
    addListener('scroll', this.detectInViewport)
    addListener('resize', this.detectInViewport)
}

detectInViewport = () => {
    const { top, bottom, height } = this.innerRef.getBoundingClientRect()
    // Calculate if on screen and distance from the viewport...
    this.setState({ inViewport: viewportPosition, viewportHeight, distanceFromViewport })
}