Update collection with an array in firebase - firebase

Question

I need to update a collection in values like this :
{
"email" : "x#gmail.com",
"fullName" : "Mehr",
"locations" : ["sss","dsds","adsdsd"]
}
Locations needs to be an array. in firebase how can I do that ... and also it should check duplicated.
I did like this :
const locations=[]
locations.push(id)
firebase.database().ref(`/users/ + ${userId}`).push({ locations })

Answer 1

Since you need to check for duplicates, you'll need to first read the value of the array, and then update it. In the Firebase Realtime Database that combination can is done through a transaction. You can run the transaction on the locations node itself here:
var locationsRef = firebase.database().ref(`/users/${userId}/locations`);
var newLocation = "xyz";
locationsRef.transaction(function(locations) {
if (locations) {
if (locations.indexOf(newLocation) === -1) {
locations.push(newLocation);
}
}
return locations;
});
As you can see, this loads the locations, ensures the new location is present once, and then writes it back to the database.
Note that Firebase recommends using arrays for set-like data structures such as this. Consider using the more direct mapping of a mathematical set to JavaScript:
"locations" : {
"sss": true,
"dsds": true,
"adsdsd": true
}
One advantage of this structure is that adding a new value is an idempotent operation. Say that we have a location "sss". We add that to the location with:
locations["sss"] = true;
Now there are two options:
"sss" was not yet in the node, in which case this operation adds it.
"sss" was already in the node, in which case this operation does nothing.
For more on this, see best practices for arrays in Firebase.

Answer 2

you can simply push the items in a loop:
if(locations.length > 0) {
var ref = firebase.database().ref(`/users/ + ${userId}`).child('locations');
for(i=0; i < locations.length; i++) {
ref.push(locations[i]);
}
}
this also creates unique keys for the items, instead of a numerical index (which tends to change).

Answer 3

You can use update rather than push method. It would much easier for you. Try it like below
var locationsObj={};
if(locations.length > 0) {
for(i=0; i < locations.length; i++) {
var key= firebase.database().ref(`/users/ + ${userId}`).child('locations').push().key;
locationsObj[`/users/ + ${userId}` +'/locations/' + key] =locations[i];
}
firebase.database().ref().update(locationsObj).then(function(){// which return the promise.
console.log("successfully updated");
})
}
Note : update method is used to update multiple paths at a same time. which will be helpful in this case, but if you use push in the loop then you have to wait for the all the push to return the promises. In the update method it will take care of the all promises and returns at once. Either you get success or error.