hulu-medium-tut-slider.js

slideLeft(index) {
    const { catWidth } = this.state;
    let slideTo = 0;
    for (let i = 0; i < index; i++) {
      slideTo += catWidth[i] + 40;
    }
    this.setState({
      toLeft: slideTo * -1 + 40,
      currentSlideIndex: index,
      currentItem: 0
    });
  }