Object.create没有创建属性

Question

I have the following function

const Admins = function(users, affiliation) {
    this.users = users;
    this.affiliation = affiliation;
}
Admins.prototype.filterAffiliation = function _filterAffiliation() {
    const filtered = this.users.filter( (user) => {
        return user.affiliation === this.affiliation;
    });
    console.log(filtered); // this shows the array of users filtered
    return Object.create(this, { users: filtered });
}

const admins = new Admins(users, affiliation);
console.log(admins);  // this shows everything correctly... 
admins.filterAffiliation() // this shows { users: undefined }

If I change the Object.create(this, {users: filtered}) with this.users = filtered; return this; this.users = filtered; return this; it "works", but I don't want to change the state of my original object. Any thoughts?

Answer 1

The "properties" optional argument to Object.create() should not be just an ordinary object. Instead, it should look like the argument to Object.defineProperties() :

   return Object.create(this, {
     users: { value: filtered }
   });

And if you want the property to be enumerable and writable etc, you have to explicitly mention that:

   return Object.create(this, {
     users: { 
       value: filtered,
       enumerable: true,
       writable: true
     }
   });

As is pointed out in a comment below, having that function return a new object created with the called context as the prototype sure looks strange. I'm not sure why you wouldn't just

   return new Admin(filtered, this.affiliation);

or something else less exotic.