Big O in JS: The basic that you need to know, see more at: https://medium.com/p/a5abb45570fa

printItemAndNextO2.js

const printItemAndNext = (...items) =>
  items.forEach((item, index) =>
    items.forEach(
      (innerItem, innerIndex) =>
        innerIndex === index + 1 && console.log(item, innerItem),
    ),
  );

/* will return: 
  1 2
  2 3
  3 4
  */
printItemAndNext(1, 2, 3, 4);