code: function findByPrototype(ary, proto) {
    var i, len, item;
    for (i = 0, len = ary.length; i < len; i++) {
      item = ary[i];
      if (proto.isPrototypeOf(item)) {
        return item;
      }
    }
  }
docs: Internal: Find first item in Array that is a prototype of `proto`.  ary   - Array of objects proto - Prototype of expected item in `ary`  Returns object from `ary` if found. Otherwise returns undefined.