README.md

Implement a compression algorithm that will count letters, e.g. coooooobalt => c6xobalt (or: 1xc6xo1xb1xa1xl1xt) stttartuuuup => s3xtart4xup (or: 1xs3xt1xa1xr1xt4xu1xp)

Use the language/technology you feel strong in.

solution.js

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"))