code: function each(obj, iterator, context) {
      var i;
  
      if (!obj) {
          return;
      }
  
      if (obj.forEach) {
          obj.forEach(iterator, context);
      } else if (obj.length !== undefined) {
          i = 0;
          while (i < obj.length) {
              iterator.call(context, obj[i], i, obj);
              i++;
          }
      } else {
          for (i in obj) {
              obj.hasOwnProperty(i) && iterator.call(context, obj[i], i, obj);
          }
      }
  }
docs: walk objects and arrays
  @param {Object} obj
  @param {Function} iterator
  @param {Object} context