gistfile1.js

function say(str, iterations) {
  let total = str;

  for (let i = 0; i < iterations; i++) {
    let count = 0;
    let output = '';

    for (let i = 0; i <= total.length; i++) {
      if (i === 0 || total[i] === total[i - 1]) {
        count = count + 1;
      } else {
        output = `${output}${count}${total[i - 1]}`;
      }
    }

    total = output;
  }

  return total;
}

console.log(
  say('1', 1),
  say('1', 2),
  say('1', 3),
  say('1', 4),
  say('1', 5)
);