Firebase Realtime Database For Web Tutorial + Video Youtube

const database = firebase.database();
const usersRef = database.ref('/users');
addBtn.addEventListener('click', e => {
  e.preventDefault();
  usersRef.child(userId.value).set({
    first_name: firstName.value,
    last_name: lastName.value,
    age: age.value
  });
});

{
   "rules": {
     ".read": true,
     ".write": true
   }
 }

const database = firebase.database();
const usersRef = database.ref('/users');
addBtn.addEventListener('click', e => {
  e.preventDefault();
  const autoId = usersRef.push().key
  usersRef.child(autoId).set({
    first_name: firstName.value,
    last_name: lastName.value,
    age: age.value
  });
});

Perbaharui data

const database = firebase.database();
const usersRef = database.ref('/users');
updateBtn.addEventListener('click', e => {
  e.preventDefault();
  const newData = {
      first_name: firstName.value,
      last_name: lastName.value,
      age: age.value
  };
  usersRef.child(userId.value).update(newData);
});

const database = firebase.database();
const usersRef = database.ref('/users');
addBtn.addEventListener('click', e => {
  e.preventDefault();
  const newData = {
      first_name: firstName.value,
      last_name: lastName.value,
      age: age.value
  };
  const autoId = usersRef.push().key;
  const updates = {};
  updates['/users/' + autoId] = newData;
  updates['/super-users/' + autoId] = newData;
  database.ref().update(updates);
});

const database = firebase.database();
const usersRef = database.ref('/users');
removeBtn.addEventListener('click', e => {
    e.preventDefault();
    usersRef.child(userId.value).remove();
});

const database = firebase.database();
const usersRef = database.ref('/users');
removeBtn.addEventListener('click', e => {
    e.preventDefault();
    usersRef.child(userId.value).remove()
    .then(()=> { console.log('User Deleted !'); })
    .catch(error => { console.error(error); });
});

const database = firebase.database();
const usersRef = database.ref('/users');
usersRef.on('child_add', snapshot => {
    console.log('Child added !');
});

const database = firebase.database();
const usersRef = database.ref('/users');
usersRef.on('child_changed', snapshot => {
    console.log('Child updated !');
});

const database = firebase.database();
const usersRef = database.ref('/users');
usersRef.on('child_removed', snapshot => {
    console.log('Child removed !');
});

const database = firebase.database();
const usersRef = database.ref('/users');
usersRef.on('value', snapshot => {
    console.log('An event occured !');
});

const database = firebase.database();
const usersRef = database.ref('/users');
usersRef.once('child_removed', snapshot => {
    console.log('Child removed !');
});

const database = firebase.database();
const usersRef = database.ref('/users');
usersRef.on('child_added', snapshot => {
    console.log(snapshot.val());
});

{
    users: {
        -Ln71n0f3c5pndQie2fo: {
            age: 32,
            first_name: "Adelina",
            last_name: "Pasaribu"
        },
        -Lt51n0f3c5pndRie2fp: {
            age: 28,
            first_name: "Wilson",
            last_name: "Pasaribu"
        },
        -Zt71n0f366pndQie2fo: {
            age: 24,
            first_name: "Elisabeth",
            last_name: "Pasaribu"
        },
        -Mt29nf03c5pndQie23f: {
            age: 30,
            first_name: "Awiel",
            last_name: "Pasaribu"
        }
    }
}

usersRef.orderByKey().limitToLast(2).on('value', snapshot => {
    console.log(snapshot.val());
});

usersRef.orderByChild('age').limitToFirst(2).on('value', snapshot => {
    console.log(snapshot.val());
});

usersRef.orderByChild('first_name').startAt('P').on('value', snapshot => {
    console.log(snapshot.val());
});

usersRef.orderByChild('last_name').equalTo('Doe').on('value', snapshot => {
    console.log(snapshot.val());
});

{
  communities: {
    com1: 265,
    com2: 700,
    com3: 20,
    com4: 301,
    com5: 532
  }
}

usersRef.orderByValue().limitToFirst(3).on('value', snapshot => {
    console.log(snapshot.val());
});

Kesimpulan