How to return a variable from a function?

Question

JavaScript

codepen
I'm trying to make a slider with auto scrolling. I want to implement it in such a way that there is a variable with the current slide and a function (called by setInterval) that takes this variable, changes the slide to the next one and increments the variable with the slide number by 1. The essence of the question is how to return this variable in order to use it when the next call to the setInterval function? I know about return, but I don't understand how to apply it here
. Or maybe I'm doing everything fundamentally wrong and there is an easier way? I didn't come up with anything (Thanks in advance.

Answer 1

It would be more correct to take out the functions in the prototype and use the instance properties for the state:

function Slider(props) {
  /* ...  */
  this.images = props.images;
  this.currentSlide = 1;
  /* ...  */
}

Slider.prototype.changeSlide = function() {
  /* ...  */
  if (this.currentSlide === this.images.length) {
    currentSlide = 1;
  } else {
    this.currentSlide++;
  }
  /* ...  */
}