import initial from "lodash/initial";
import last from "lodash/last";

export const group = (stack, value) => {
  const [letter, total] = last(stack) || [null, 0];
  const chained = letter === value;
  const next = [[value, chained ? total + 1 : 1]];

  return chained ? initial(stack).concat(next) : stack.concat(next);
};

export const format = (stack, [letter, total]) =>
  stack.concat(total > 1 ? `${total}x` : [], letter);

export const compress = (object) => {
  const collection = String(object).split("");
  const groups = collection.reduce(group, []);

  return groups.reduce(format, "");
};

console.log(compress("coooooobalt"))
console.log(compress("stttartuuuup"))