how to read specific data from realtime database in node.js

Question

I am working on API Get request. I have created a POST request to add the data in firebase realtime database. The code is as follows:

// CREATE POST
app.post("/post", (req, res) => {
  let key;

firebase.auth().onAuthStateChanged((user) => {
if (user) {
  // User is signed in.

  var newPost = firebase.database().ref("posts/");

  var myPost = newPost.push({
    createdBy: user.uid,
    from: req.body.from,
    to: req.body.to,
    duration: req.body.duration,
    comments: req.body.comments,
  });

  res.send(newPost);
  const postId = myPost.key;
  console.log(postId);
} else {
  // No user is signed in.
  res.status(404).send("No user is signed in right now!");
}
  });
});

Now, in order to get a specific post, I have written the following code:

// GET SPECIFIC POST
app.get("/post/:id", (req, res) => {

  let response;
  firebase
    .database()
    .ref("posts/" + req.params.id)
    .on("value", (snapshot) => {
      response = snapshot.val();
    });
  res.send(response);
});

I am new at Firebase, so I dont really know how to get a specific post. Please help me out

score 1 · Accepted Answer · answered Jun 02 '21 at 14:21

Calls to Firebase are asynchronous, because they require a call to the server. While that call is happening, your main code continues. And then when the data is available, your callback is invoked with the data from the server.

Right now your res.send(response) runs before the response = snapshot.val() is ever called. The rule with asynchronous APIs is simple: any code that needs the data needs to be inside the callback, or be called from there.

So in your case:

app.get("/post/:id", (req, res) => {
  firebase
    .database()
    .ref("posts/" + req.params.id)
    .once("value")
    .then((snapshot) => {
      res.send(snapshot.val());
    });
});

You'll note that I also change from on to once, since you only care about getting the value once (instead of attaching a permanent listener that monitors the database for changes).

Dealing with asynchronous API is a common stumbling block, so I recommend spending some time reading these answers to learn more:

I tried your solution. Thanks for that, but the issue is when i am running it on postman as http://localhost:4242/post/MbC2aBbai02KKYUus1s where the hashcode is the key of a post, I donot get anything in my response — Adeena Lathiya, Jun 02 '21 at 14:31
this just renders all the posts as if i am creating a GET request to show all the posts — Adeena Lathiya, Jun 02 '21 at 16:57
That sounds like your `req.params.id` is empty. You might want to `console.log(req.params.id)` to verify that. — Frank van Puffelen, Jun 02 '21 at 18:49

score 0 · Answer 2 · answered Jun 03 '21 at 12:15

0

I simply did this:

app.get("/post/:id", (req, res) => {

var key = req.params.id;
  console.log(key);

 firebase
    .database()
    .ref("posts")
    .child(key)
    .get()
    .then((snapshot) => {
      res.send(snapshot.val());
    });
});

this solved the problem

answered Jun 03 '21 at 12:15

Adeena Lathiya

165
1
11

Is that for FireStore or Firebase realtime DB? – Learn2Code Aug 06 '22 at 03:04
For firebase Cloud firestore – Adeena Lathiya Aug 06 '22 at 16:24
Im confused, you first asked about how to read specific data from realtime database in node.js and then you answered your own question on how to read data from FireStore instead? – Learn2Code Aug 06 '22 at 18:32
Sorry, Some glitch from my side. Ny problem got resolved. Thank you – Adeena Lathiya Aug 07 '22 at 17:49

how to read specific data from realtime database in node.js

2 Answers2