JSFiddle - React, Tailwind, and code Playground

by Eugen Sunic

JavaScript

const word = 'aabbbccccaaaaa';
let output = '';
let counter = 0;

for (let i = 0; i < word.length; i++) {
  const current = word[i];
  const next = word[i + 1];
  output += current;
  counter++;
  if (current !== next) {
    output += counter;
    counter = 0;
  }
}
console.log(output);