var createdImages = [ ];

class Slider extends Component{
  constructor(props){
    super();
    this.state = {
      imagesArray : ['css', 'html', 'javascript'],
      slide : 0
  };
};

  creatingImages() {

   return createdImages =  this.state.imagesArray.map((image, index) => {
      return <img key={image}
      className={index === 0 ? 'active' : ''}
      src={require(`./img/${image}.png`)} />
   });
  }

startSlider() {

  createdImages[this.state.slide % 3].setAttribute("class", " ");
  createdImages[(this.state.slide) % 3].setAttribute("class", "active");
  this.setState(prevState => ({
    slide : prevState.slide + 1
  }));
};

  componentDidMount(){
    this.sliderInterval = setInterval( () => this.startSlider(), 2500);
  }