var postRef = db.collection("posts").doc(this.docID);
postRef.get().then(function(doc) {
if (doc.exists) {
var contentRef = db.collection("content").doc(doc.id)
contentRef.get().then(function(doc) {
....
}
} else {
// doc.data() will be undefined in this case
console.log("No such document!");
}
}).catch(function(error) {
console.log("Error getting document:", error);
});