function contains(haystack, needle) {
  return haystack.indexOf(needle) !== -1;
}

function commatize(text, start_index = 0, step = 3, separator = ",") {
  console.log("Before: " + text);
  const size = text.length;

  for (let i = start_index; i < size; ++i) {
    if (contains("123456789", text[i])) {
      for (let j = i + 1; j <= size; ++j) {
        if (j > size || !contains("0123456789", text[j])) {
          for (let k = j - 1 - step; k >= i; k -= step) {
            text = text.slice(0, k + 1) + separator + text.slice(k + 1);
          }
          break;
        }
      }
      break;
    }
  }

  console.log(" After: " + text + "\n");
}

function main() {
  commatize("pi=3.14159265358979323846264338327950288419716939937510582097494459231", 6, 5, " ");
  commatize("The author has two Z$100000000000000 Zimbabwe notes (100 trillion).");
  commatize("\"-in Aus$+1411.8millions\"");
  commatize("===US$0017440 millions=== (in 2000 dollars)");
  commatize("123.e8000 is pretty big.");
  commatize("The land area of the earth is 57268900(29% of the surface) square miles.");
  commatize("Ain't no numbers in this here words, nohow, no way, Jose.");
  commatize("James was never known as 0000000007");
  commatize("Arthur Eddington wrote: I believe there are " +
             "15747724136275002577605653961181555468044717914527116709366231425076185631031296" +
             " protons in the universe.");
  commatize("   $-140000±100 millions.");
  commatize("6/9/1946 was a good year for some.");
}

main();