code: function findAllIndices(needle = mandatory(), haystack = mandatory()) {
    var indices = [];
    for (var i = 0; i < haystack.length; i++) {
      if (haystack.substr(i, needle.length) === needle) {
        indices.push(i);
      }
    }
  
    if (indices.length) {
      return indices;
    } else {
      return -1;
    }
  }
docs: Find all the positions of a needle in a haystack string
  @param  {string} needle   string to find
  @param  {string} haystack string to scan
  @return {Array}  Either -1 if no match is found or an array containing the indicies