Firebase更新特定字段？

Question

Im updating my firebase database continuously with this code:

var admin = require("firebase-admin");


// Fetch the service account key JSON file contents
var serviceAccount = require("service.json");

// Initialize the app with a service account, granting admin privileges

admin.initializeApp({
  credential: admin.credential.cert(serviceAccount),
  databaseURL: "DATABASE_URL"

});

var db = admin.database();
var ref = db.ref("games");

var fs = require('fs');
var filePath = 'games/2017-06-27.json';
var file = fs.readFileSync(filePath);

fs.watchFile(filePath, function() {

var request = require('request');

var usersRef = ref.child('2017-06-27');



request('http://URL/games/2017-06-27.json', function (error, response, body) {
  if (!error && response.statusCode == 200) {

    var asJson = JSON.parse(body)


    usersRef.update(asJson)

   }
})

});

So I get a json with real-time sports data scores, game status etc (using another service). I then use node to check changes on the file where the data is stored and write to the firebase database. It works fine, but I don't want to replace the DB. I just want to update the fields that change, because I have other service adding extra data to this child in the database that i want to keep. How can I update only the fields with changes without replacing the all Database and that way keep other extra data that don't come from this request?

Answer 1

When you call update() on a location, Firebase loops over the data that you pass in (in your case asJson ) and for each key performs a ref.child(key).set(value) .

Object.keys(asJson).forEach((key) => {
  usersRef.child(key).set(asJson[key]);
})

So while it merges the top-level properties of asJson with the existing data under usersRef , it still replaces the data under each key.

If you want to merge on that level too, you'll have to convert the JSON from a tree into a list of paths. Say your JSON looks like this:

{
  user1: {
    name: "Speed_John"
  },
  user2: {
    name: "Frank van Puffelen"
  }
}

You will have to convert this to:

{
  "user1/name": "Speed_John",
  "user2/name": "Frank van Puffelen"
}

 var JSON = { user1: { name: "Speed_John" }, user2: { name: "Frank van Puffelen", id: 209103 } }; var updates = {}; function flatten(json, prefix) { Object.keys(json).forEach((key) => { var path = (prefix||"")+"/"+key; if (typeof json[key] === "object") { flatten(json[key], path); } else { updates[path] = json[key]; } }); } flatten(JSON); console.log(updates); 

With this code you can then call:

usersRef.update(updates);