How to retrieve nested child value in Firebase database using javaScript?

Question

Here is my Fireabse database structure. I want to retrieve data of 20170116 keys that is not a hard coded value. It's dynamic keys. I got some keys and values like :

This is my funtion :

function getData(prospectId) {
    database.ref('users/'+prospectId).once('value').then(function(snapshot) {
        var prospectId = snapshot.key ;
        console.log("prospectId : "+ prospectId); // output is : prospectId : 1104812

        snapshot.forEach(function(childSnapshot) {
            var businessUrl = childSnapshot.key;
            console.log("businessUrl : "+ businessUrl); // output is : businessUrl : http:\\www.abc.com
            var dates = Object.keys(childSnapshot.val());
            console.log("dates : "+ dates); //output is : dates : 20170116,20170117,20170119,20170121
            var singleDate = dates[0];
            console.log("singleDate : "+ singleDate); //output is : singleDate : 20170116
        });
    });
}  

getData(1104812);

So how to get 20170116 date data or snapshot ?

Educated guess below. If that's not it (and for future questions) please replace the picture of JSON with the actual JSON as text, which you can easily get by clicking the Export JSON link in your Firebase Database console. Having the JSON as text makes it searchable, allows us to easily use it to test with your actual data and use it in our answer and in general is just a Good Thing to do. — Frank van Puffelen
– Frank van Puffelen, Commented Jan 28, 2017 at 18:32

Frank van Puffelen · Accepted Answer · 2017-01-30 09:19:53Z

5

You're attaching a value listener to /users/1104812. So the snapshot you get in your callback will contain the child nodes under that: 20170116, 20170117 and 20170119.

When you loop over the children (with snapshot.forEach(function() your childSnapshot will become each of those nodes in turn.

None of these nodes has a child clientUrl or districtId, those are one level deeper into the tree:

database.ref('users/'+prospectId).once('value').then(function(snapshot) {
  var prospectId = snapshot.key ;

  snapshot.forEach(function(snapshot1) {
    console.log(snapshot1.key); // e.g. "http://..."
    snapshot.forEach(function(snapshot2) {
      console.log(childSnapshot.key); // e.g. "20170116"
      childSnapshot.forEach(function(snapshot3) {
        console.log(grandchildSnapshot.key); // e.g. "-Kb9...gkE"
        console.log(grandchildSnapshot.val().districtId); // "pne"
      });
    });
  });
});

edited Jan 30, 2017 at 9:19

answered Jan 28, 2017 at 18:31

Frank van Puffelen

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2 Comments

Menu Over a year ago

whatever you written in the code I have logged the value and its printed undefined. Here console.log(childSnapshot.key) this line is printed http:\\www..., console.log(grandchildSnapshot.key) this is printed 20170116, ` console.log(grandchildSnapshot.val().districtId)` this is printed undefined.

Frank van Puffelen Over a year ago

Yeah, it looks like you have yet another level around it in the JSON. I updated the code to add another block.

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