How to upload multiple files to Firebase?

Is there a way to upload multiple files to Firebase storage. It can upload single file within single attempt as follows.

fileButton.addEventListener('change', function(e){ 
//Get file
var file = e.target.files[0];

//Create storage reference
var storageRef = firebase.storage().ref(DirectryPath+"/"+file.name);

//Upload file
var task = storageRef.put(file);

//Update progress bar
  task.on('state_changed',
    function progress(snapshot){

        var percentage = snapshot.bytesTransferred / snapshot.totalBytes * 100;
        uploader.value = percentage;
    },
    function error(err){

    },
    function complete(){
        var downloadURL = task.snapshot.downloadURL;

    }
  );

});

How to upload multiple files to the Firebase storage.

Answer

I found the solution for my above question and I like to put it here because it can be useful for anyone.

//Listen for file selection
fileButton.addEventListener('change', function(e){ 
    //Get files
    for (var i = 0; i < e.target.files.length; i++) {
        var imageFile = e.target.files[i];

        uploadImageAsPromise(imageFile);
    }
});

//Handle waiting to upload each file using promise
function uploadImageAsPromise (imageFile) {
    return new Promise(function (resolve, reject) {
        var storageRef = firebase.storage().ref(fullDirectory+"/"+imageFile.name);

        //Upload file
        var task = storageRef.put(imageFile);

        //Update progress bar
        task.on('state_changed',
            function progress(snapshot){
                var percentage = snapshot.bytesTransferred / snapshot.totalBytes * 100;
                uploader.value = percentage;
            },
            function error(err){

            },
            function complete(){
                var downloadURL = task.snapshot.downloadURL;
            }
        );
    });
}