Firebase 101

firebase.md

Firebase 101

import * as firebase from 'firebase';

const config = {
    apiKey: "XXXXXXXXXXXXX",
    authDomain: "XXXXXXXXm",
    databaseURL: "XXXXXXXXm",
    projectId: "expXXXXXXXXXXXXXXX39",
    storageBucket: "expXXXXXXXXXXXXXXXXom",
    messagingSenderId: "XXXXXXXXX"
};
firebase.initializeApp(config);

const database = firebase.database();

SET OR INSERT INTO DB

database.ref().set({
    name: "Ashish",
    age: 10,
    attributes: {
        height: 12,
        width: 13
    }
})

REMOVE FROM DB

database.ref('attributes/width').remove();

UPDATE FROM DB

Takes always an object

database.ref().update({
    name: "Ashish Verma",
    age: 26,
    'attributes/height': 33 // to remove field with update or set - value is null
})

READ FROM DB

METHOD 1 -> Get Value only Once

database.ref()
    .once('value')
    .then((snapshot) => console.log(snapshot.val()))
    .catch((e) => console.log('error', e));

METHOD 2 -> Subscribe to changes

when any value gets changed - returns all

database.ref()
    .on('value',
        (snapshot) => console.log(snapshot.val()), 
        (e) => { console.log("Error", e) }
    )

when any child is deleted - returns deleted one

database.ref()
    .on('child_removed',
        (snapshot) => console.log(snapshot.val()), 
        (e) => { console.log("Error", e) }
    )

when any child is changed - returns changed one

database.ref()
    .on('child_changed',
        (snapshot) => console.log(snapshot.val()), 
        (e) => { console.log("Error", e) }
    )

when any child is added - returns new children plus the existing ones

database.ref()
    .on('child_added',
        (snapshot) => console.log(snapshot.val()), 
        (e) => { console.log("Error", e) }
    )

METHOD 2.1 -> Un-Subscribe All changes

database.ref().off()

METHOD 2.2 -> Un-Subscribe Some changes

const onValueChange = database.ref()
    .on('value', (snapshot) => {
        console.log(snapshot.val())
    }, (e) => { console.log("Error", e) })

setTimeout(() => {
    console.log(onValueChange);
    database.ref().off('value', onValueChange);
    database.ref('attributes/height').set(25);
}, 5000)

Storing List

Firebase doesnt support Arrays

So to deal with it we can use something like

database.ref('notes').push({
    title: 'Learn Firebase',
    body: 'realtime DB is cool!'
})

This command creates the object under random key insides notes.

notes
    -L-uxrYE5LSUGBgbhBjl
        body: "realtime DB is cool!"
        title: "Learn Firebase"