Polymer Firebase. Arrays in Objects

Im using polymer and firebase and I was wondering how to create an array of objects inside an object.

I want nested data like in the object the groups single object whereby we have members and the names inside it

      this.$.query.ref.push({
        name: this.$.crewName.value,
        description: this.$.crewDescription.value,
        createddate: new Date().toString(),
        creator: this.$.createcrewlogin.user.uid,
        slug: sluggedname
      });

With a simple push method like this .How do I achieve that

When you write to the Firebase Database from JavaScript, you pass in a standard JSON object. This means that you can just nest the objects inside the object you pass to push():

  this.$.query.ref.push({
    name: this.$.crewName.value,
    description: this.$.crewDescription.value,
    createddate: new Date().toString(),
    creator: this.$.createcrewlogin.user.uid,
    slug: sluggedname,
    subobject: {
      techpioneers: true,
      womentechmakers: true
    }
  });