Return the index of all instances of an item in an String

indexOfAll.js

String.prototype.indexOfAll = function(s){

  // Make sure it's 1 char, use first char of string.
  s = s[0];


  var results = [],
      result = null,
      i = 0,
      offset = 0,   // Incremented by previous index
      // Copy as to not modify.
      temp = this.slice(0),
      len = temp.length;

  for(; i < len; i++){
    result = temp.indexOf(s);

    if(result > -1){
      results.push(result + offset);
      offset += result + 1;

      // Slice at cursor position (index of last item) + 1
      temp = temp.slice(result + 1);

      // Reset loop to operate on new length
      len = temp.length;
    }
  }

  return results;

};