How to properly do something onUpdate of firebase realtime database?

Question

Why Am I getting error in this code block?

var current_op_id = 0;

var targetRef = firebase.database().ref('operators/' + current_op_id);

    targetRef.onUpdate((change, context) => {
        //do something here
    });

Error: Uncaught TypeError: targetRef.onUpdate is not a function

Just before that code block, I have this code block that works OK.

var op_id = 0;

var updatedRef = firebase.database().ref('operators/' + op_id);

    updatedRef.on('value', function(snapshot) {
        //do something here

    });

Answer 1

onUpdate() is used in cloud functions, from the docs :

onUpdate() , which triggers when data is updated in the Realtime Database.

exports.dbUpdate = functions.database.ref('/path').onUpdate((change, context) => {
  const beforeData = change.before.val();
  const afterData = change.after.val(); 
});

If you want to update a field in Realtime Database, then you need to use update() . You can read more about it here:

https://firebase.google.com/docs/database/web/read-and-write#update_specific_fields