Use the modulo operator for a looping slide show

modulo-for-slide-show-loop.js

// When making a looping slide show, here's the long way to get at what the modulo operator provides

if (counter < images.length - 1) {
  counter++;
} else {
  counter = 0;
}

const prevIndex = counter < 1 ? images.length - 1 : counter - 1;
const currIndex = counter;
const nextIndex = counter == images.length - 1 ? 0 : counter + 1;

// Modulo

const prevIndex = (counter - 1 + images.length) % images.length)
const nextIndex = (counter + 1) % images.length;