JSFiddle - React, Tailwind, and code Playground

by krustnic

JavaScript

let s = "AAAAAAAABBBBBCCCCCDDDDXYZ"

function f(s) {
	return s.match(/(.)\1*/g).reduce((out, item) => {
  	out += item[0] + (item.length === 1 ? '' : item.length)
  	return out
  }, '')
}

console.log(f(s))