Need to push object into firebase array with val()

Question

I've recently gotten started with Firebase development in React.js -

At the moment, I'm trying to pull from the database and create a new object with the data.

This is the code:

var arr = firebase.database().ref("news");//this is the ref.

arr.once('value', function (snapshot) {//will return the array value
    model = {//this is the model i want to .push()
        title: title,
        content: content,
        img: img,
        category: category,
        likes: likes,
        id: snapshot.val().length//This is where I want to add the arr.length
    };

    var promise = arr.push(model);

    promise.then(function(){
        ...
    })
})

The problem is that arr.push(model) runs BEFORE the model.id variable is loaded.

snapshot.val() get you a javascript object. do you want to get how many children in it? — Hareesh
– Hareesh, Commented Mar 27, 2018 at 13:32
@Luis I’ve tried that but it wont work either! Maybe calling an ‘on’ function when the array.val() is called? Don’t know how to implement it.. — skpdm
– skpdm, Commented Mar 27, 2018 at 13:32
The array.push is called before the snapshot.val()... .val() is asymchronous :( — skpdm
– skpdm, Commented Mar 27, 2018 at 13:38

Meghashyam Bhandary · Accepted Answer · 2018-03-27 22:31:00Z

1

What happens here is snapshot.val() returns a object and not a array. Hence, it would return undefined if u try to access snapshot.val().length.

Now the solution is to convert object to array to get the count.

id: Object.keys(snapshot.val()).length

This might solve your problem.

Sorry if this is not what you are looking for.

answered Mar 27, 2018 at 22:31

Meghashyam Bhandary

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1 Comment

Meghashyam Bhandary Over a year ago

@Hareesh, that would be a better solution.

Hareesh · Accepted Answer · 2018-03-28 04:56:28Z

0

@Meghashyam solution should work. Firebase also have a utility snapshot.numChildren(); which will return number of child properties of this DataSnapshot, if object is empty it will return 0

model = {
    title: title,
    content: content,
    img: img,
    category: category,
    likes: likes,
    id: snapshot.numChildren()
};

You can check more details here

answered Mar 28, 2018 at 4:56

Hareesh

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