javascript - 检查对象是否是 mongo 游标

Question

我有一个方法，我想接收列表或 mongo 游标并对此使用react，例如:

createFromTemplate: function(template) {
  var iter;
  if(template instanceof Mongo.Cursor) {
    iter = template.fetch();
  } else if(template instanceof Array) {
    iter = template;
  } else {
    throw new Meteor.Error(500, 'Template must be a Cursor or Array');
  }
}

但是，当我没有预料到时，它似乎返回 false

> var p = PageTemplates.find();  // as a mongo cursor
> var pArray = p.fetch();        // as an array
> Object.prototype.toString.call(p);
[object Object]
> typeof p
Object
> p instanceof Mongo.Cursor
false

如何判断一个对象是否是 Mongo 游标？

Answer 1

您应该能够使用instanceof Mongo.Collection.Cursor(而不是Mongo.Cursor)。从我的控制台:

> a = Meteor.users.find()
<- LocalCollection.Cursor {collection: LocalCollection, sorter: null, _selectorId: undefined, matcher: Minimongo.Matcher, skip: undefined…}
> a instanceof Mongo.Collection.Cursor
<- true