如何链接两个JavaScript对象？

Question

Say I have an object (obj1) where one of the values in obj1 is another object (obj2). Is there any way to make it so that checking for anything in obj1 (eg obj1.username) would also check in obj2 (obj1.ob2.username) automatically?

The use case for this is if something doesn't exist in obj1, I would want to also check in obj2 before it returns null.

Example Usage:

 var user = {username: "David"} // obj2 var member = {nickname: "Dave", user: user} // obj1 console.log(user.username) // "David" console.log(user.nickname) // null console.log(member.username) // "David" console.log(member.nickname) // "Dave" 

This is for usage in Node.js.

--Edit--

I forgot to note that members and users are created from classes in a library I'm using to interact with an application called Discord.

When a message is sent an event is triggered and I am handed information like the member object (with a link to the user object inside it).

Here is the structure of a user.

Here is the structure of a member.

Object.defineProperty(Discord.Member.prototype, 'username', {
    get: function() { return this.user.username; },
    set: function(newValue) { this.user.username = newValue; }
});

The above method works as intended, however only for the username property. I considered applying this for every property of user, however when I tried iterating through the properties of a created user, some (like .createdAt ) didn't show up in the list.

I understand that I could do it manually and write every defineProperty by hand, but the idea here is that user will be constantly updated with new properties over time, so I would prefer it to do what I described above.

Answer 1

You could use Proxy and inside use getter to check first if property exists in original and then in other object.

 var user = { username: "David" } // obj2 var member = { nickname: "Dave", user: user, } // obj1 var pMember = new Proxy(member, { get: function(target, prop) { if (target[prop]) return target[prop]; else if (target.user[prop]) return target.user[prop]; } }); console.log(pMember.nickname) console.log(pMember.username) 

Answer 2

Using inheritance:

var user = {username: "David"} // obj2
var member =Object.assign(Object.create(user),{nickname: "Dave", user: user}); // obj1

console.log(member.username);

http://jsbin.com/nojolizewu/edit?console