replaceZeros.ts

function replaceZeros(input: string): number {
  let zeroes = 0;

  const res = input
    .split("")
    .reduce((acc: string[], curr, index, digits) => {
      const next = digits[index + 1];

      if (curr === "0" && next === "0") {
        zeroes++;
      } else if (curr === "0" && next !== "0") {
        zeroes++;
        acc.push(zeroes.toString());
        zeroes = 0;
      } else {
        acc.push(curr);
      }

      return acc;
    }, []);

  return parseInt(res.join(""));
}

import { assertEquals } from "https://deno.land/std@0.168.0/testing/asserts.ts";

Deno.test("test 1", () => {
  const res = replaceZeros("1234500362000440");
  assertEquals(res, 1234523623441);
});

Deno.test("test 2", () => {
  const res = replaceZeros("123450036200044");
  assertEquals(res, 123452362344);
});

Deno.test("test 3", () => {
  const res = replaceZeros("000000000000");
  assertEquals(res, 12);
});

Deno.test("test 4", () => {
  const res = replaceZeros("123456789");
  assertEquals(res, 123456789);
});