Filtering object in Javascript react-native

Question

I have this structure of data: This is source code of my chats component: https://pastebin.com/JJQFQyHi

every chat has two members, I want to display other persons data profile_picture and username in my chat list. So i want to delete unnecessary data. I use firebase realtime database. This is how i tried to rid off unnecessary data.

getChats = _userId => {
    let data;
    var readedData = firebase
      .database()
      .ref('chats')
      .orderByChild('members/' + _userId)
      .equalTo(true);
    readedData.once('value', snapshot => {
      this.setState({ chats: snapshot.val() });
      // console.log(JSON.stringify(this.state.chats));
      data = snapshot.val();
      delete data._userId;
      delete data.members;
      console.log(data);
    });
  };

console log:

> {"-M4NzlagjmeFH7IR_Api": {"lwcIQTcpAae4e38hrD2K5Ar76W93": {"data":
> [Object]}, "members": {"lwcIQTcpAae4e38hrD2K5Ar76W93": true,
> "tempuser": true}, "tempuser": {"data": [Object]}},
> "-M4O-aIxt9w2iKuCDweN": {"lwcIQTcpAae4e38hrD2K5Ar76W93": {"data":
> [Object]}, "members": {"lwcIQTcpAae4e38hrD2K5Ar76W93": true,
> "tempuser": true}, "tempuser": {"data": [Object]}},
> "-M4Q05H1lEUIyWqLJyoQ": {"lwcIQTcpAae4e38hrD2K5Ar76W93": {"data":
> [Object]}, "members": {"lwcIQTcpAae4e38hrD2K5Ar76W93": true}},
> "-M649remSnfBLBuYJIXO": {"lwcIQTcpAae4e38hrD2K5Ar76W93": {"data":
> [Object]}, "members": {"lwcIQTcpAae4e38hrD2K5Ar76W93": true,
> "tempuser": true}, "messages": {"-M64A0ydh-WJstJIFIr1": [Object],
> "-M66cLC6OjQhlyNN5uDq": [Object], "-M66eWivUodiVtHIkfGv": [Object]},
> "tempuser": {"data": [Object]}}}

Answer 1

When you refer call snapshot.val() you get an object as you have shown in the console log. This value is then assigned to data .

When you try to delete keys from this data object, Javascript tries to remove them from the top level of the object. Since there are no properties with the given names ( members or _userId ) at the top level, it fails to filter anything out.

If you need a list of tempuser s, you can build it using the forEach method of the snapshot .

readedData.once("value", (snapshot) => {
  const userData = [];
  snapshot.forEach((data) => {
    userData.push(data.tempuser)
  });

  console.log(userData); // this should contain the tempusers.
});