javascript - Firebase update or set -

after adding post person firebase database, want add reference new post person. person may or may not 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 creates node called _person in child person instead of value of _person variable. using set() overwrite existing person.

example: first node remarks/-jlkbxakpqs50w7r84gf created child node person/123456

after want create node person/123456 (only if doesn't exist) , add child node remark/-jlkbxakpqs50w7r84gf it. post-id automatically generated (firebase) person's id taken html form.

how do that?

depending on how data structured, before update, may able reference person want.

so, if data looks this:

{     "remarks" : {                    ...                 },      "person" : {                  "123456" : {                                 "name" : "foo",                                 ...                                 "blah" : "bar"                             },                  ...                } } 

and document.getelementbyid("person").value gives 123456, can reference like:

var personref = ref.child("person").child(_person); 

then want see if exists, , if does, update it:

personref.once('value', function(snapshot) {      if( snapshot.val() === null ) {         /* not exist */     } else {         snapshot.ref().update({"postid": postid});     }  });