code: function addKeyToList(list, key, object) {
      for (var i = list.length - 1; i >= 0; i--) {
          if (list[i][key] == object[key]) {
              return false;
          }
      }
      list.push(object);
      return true;
  }
docs: Add in list the argument object if none has the same key attribute
  
  @param list Array of objects having key attribute
  @param {string} key
  @param object New object to add
  @return {boolean} True if added or false if already exists in list