After adding a post about a person to a Firebase database, I want to add the reference to the new post to the person. However the person may or may not already exist.

I have:

var ref = new Firebase("https://mydatabase.firebaseio.com/");

var _person = document.getElementById("Person").value;

var _remark = document.getElementById("Remark").value;



var postsRef = ref.child("remarks");

var newPostRef = postsRef.push({

    person: _person,

    remark: _remark

});



var postID = newPostRef.key();



var personRef = ref.child("person");

personRef.update({

    _person: postID

});

However that creates a node called _person in child person instead of the value of the _person variable. Using set() would overwrite an existing person.

Example:
First a node remarks/-JlkbxAKpQs50W7r84gf is created with child node person/123456

After that I want to create a node person/123456 (only if it doesn't already exist) and than add a child node remark/-JlkbxAKpQs50W7r84gf to it. The post-id is automatically generated (Firebase) but the person's id is to be taken from a html form.

How do I do that?