【HH原创】Firebase 相关操作及代码示例

今天需要对 Firebase 增加删除功能，代码精简如下：

var admin = require('firebase-admin');
 var config = require('./config.json');
 
 var defaultAppConfig = {
     credential: admin.credential.cert(config.firebase.cert),
     databaseURL: config.firebase.databaseURL
 };
 
 
 var defaultAppName = 'GoPeople-NodeJS-Admin';
 var defaultApp = admin.initializeApp(defaultAppConfig, defaultAppName);
 
 var signaturesRef = defaultApp.database().ref('signatures');
 
     signaturesRef.orderByChild("isChecked").equalTo(true).limitToLast(10).once("value")
         .then(function(snapshot) {
 
             snapshot.forEach(function(childSnapshot) {
                 var key = childSnapshot.key;
                 var childData = childSnapshot.val();
 
                 var now = new Date();
                 var date = new Date(childData.date);
                 var dayDiff = parseInt((now - date) / (1000 * 60 * 60 * 24)); // day diff
 
                 if(dayDiff >30){
                     signaturesRef.child(key).remove(function(error) {
                         console.log(key);
                         console.log(dayDiff);
                         console.log(error ? ("Uh oh! " + error) : "Success!");
                     });
                 }else{
                     console.log(key);
                     console.log(dayDiff);
                 }
             });
 
         });

Firebase 修改节点：

function finishJobSync(jobGuid) {
    var signaturesRef = defaultApp.database().ref('signatures').child(jobGuid);
    signaturesRef.update({isChecked: true},function(error) {
        if (error) {
            logger.error(error);
        } else {
            logger.info('Job ' + jobGuid + ' signature has been synced.');
        }
    });
}

Firebase 监听：

var signaturesRef = defaultApp.database().ref('signatures');

signaturesRef.orderByChild("isChecked").equalTo(false).on("child_added", function(snapshot, prevChildKey) {
    // TODO: 
});

admin.database.DataSnapshot

>> key

// Assume we have the following data in the Database:
{
  "name": {
    "first": "Ada",
    "last": "Lovelace"
  }
}

var ref = admin.database().ref("users/ada");
ref.once("value")
  .then(function(snapshot) {
    var key = snapshot.key; // "ada"
    var childKey = snapshot.child("name/last").key; // "last"
  });

>> child

var rootRef = admin.database().ref();
rootRef.once("value")
  .then(function(snapshot) {
    var key = snapshot.key; // null
    var childKey = snapshot.child("users/ada").key; // "ada"
  });

>> exists

// Assume we have the following data in the Database:
{
  "name": {
    "first": "Ada",
    "last": "Lovelace"
  }
}

// Test for the existence of certain keys within a DataSnapshot
var ref = admin.database().ref("users/ada");
ref.once("value")
  .then(function(snapshot) {
    var a = snapshot.exists();  // true
    var b = snapshot.child("name").exists(); // true
    var c = snapshot.child("name/first").exists(); // true
    var d = snapshot.child("name/middle").exists(); // false
  });

 >> foreach

// Assume we have the following data in the Database:
{
  "users": {
    "ada": {
      "first": "Ada",
      "last": "Lovelace"
    },
    "alan": {
      "first": "Alan",
      "last": "Turing"
    }
  }
}

// Loop through users in order with the forEach() method. The callback
// provided to forEach() will be called synchronously with a DataSnapshot
// for each child:
var query = admin.database().ref("users").orderByKey();
query.once("value")
  .then(function(snapshot) {
    snapshot.forEach(function(childSnapshot) {
      // key will be "ada" the first time and "alan" the second time
      var key = childSnapshot.key;
      // childData will be the actual contents of the child
      var childData = childSnapshot.val();
  });
});

>> hasChildren

// Assume we have the following data in the Database:
{
  "name": {
    "first": "Ada",
    "last": "Lovelace"
  }
}

var ref = admin.database().ref("users/ada");
ref.once("value")
  .then(function(snapshot) {
    var a = snapshot.hasChildren(); // true
    var b = snapshot.child("name").hasChildren(); // true
    var c = snapshot.child("name/first").hasChildren(); // false
  });

>> numChildren

// Assume we have the following data in the Database:
{
  "name": {
    "first": "Ada",
    "last": "Lovelace"
  }
}

var ref = admin.database().ref("users/ada");
ref.once("value")
  .then(function(snapshot) {
    var a = snapshot.numChildren(); // 1 ("name")
    var b = snapshot.child("name").numChildren(); // 2 ("first", "last")
    var c = snapshot.child("name/first").numChildren(); // 0
  });

admin.database.Query

>> startAt, endAt

// Find all dinosaurs that are at least three meters tall.
var ref = admin.database().ref("dinosaurs");
ref.orderByChild("height").startAt(3).on("child_added", function(snapshot) {
  console.log(snapshot.key)
});

// Find all dinosaurs whose names come before Pterodactyl lexicographically.
var ref = admin.database().ref("dinosaurs");
ref.orderByKey().endAt("pterodactyl").on("child_added", function(snapshot) {
  console.log(snapshot.key);
});

>> limitToFirst, limitToLast

// Find the two shortest dinosaurs.
var ref = admin.database().ref("dinosaurs");
ref.orderByChild("height").limitToFirst(2).on("child_added", function(snapshot) {
  // This will be called exactly two times (unless there are less than two
  // dinosaurs in the Database).

  // It will also get fired again if one of the first two dinosaurs is
  // removed from the data set, as a new dinosaur will now be the second
  // shortest.
  console.log(snapshot.key);
});


// Find the two heaviest dinosaurs.
var ref = admin.database().ref("dinosaurs");
ref.orderByChild("weight").limitToLast(2).on("child_added", function(snapshot) {
  // This callback will be triggered exactly two times, unless there are
  // fewer than two dinosaurs stored in the Database. It will also get fired
  // for every new, heavier dinosaur that gets added to the data set.
  console.log(snapshot.key);
});

......