firestore code work with dropzone

firestore-code-work-with-dropzone.js

function storage_upload(filedata, filehandle, DropzoneHandle, cb) {

    // Getting Handle of the progressbar element of current file // 
    var progressBar = filehandle.previewElement.children[2]

    // Firestore storage task 
    var task
        // uuid for file being uploaded
    var uuid_string = uuid()

    // Getting Storeage referance for file 
    var storageRef = firebase.storage().ref(User.client_id + "/" + uuid_string);

    // Because I am uploading file in base64 data_url // 
    task = storageRef.putString(filedata, 'data_url');

    // Making progress bar of current file preview element visible  
    progressBar.opacity = 1

    task
        .on(firebase.storage.TaskEvent.STATE_CHANGED,

            // Trakcing progress of upload
            function progress(snapshot) {
                var progress = (snapshot.bytesTransferred / snapshot.totalBytes) * 100;

                // Updating progressbar width - to make it look like filling
                progressBar.children[0].style.width = progress + '%'

            },

            // Firebase storeage upload error handling 
            function(error) {
                // Hanlde your way
                // A full list of error codes is available at
                // https://firebase.google.com/docs/storage/web/handle-errors
            },

            // Finishing process and returing data
            // Returning file-meta and  url
            // and hiding progress bar  
            function() {

                // Upload completed successfully, now we can get the meta data of file
                task.snapshot.ref.getMetadata().then(function(meta) {
                    // Getting download url of file
                    task.snapshot.ref.getDownloadURL().then(function(downloadUrl) {

                        // storing meta data and download url in object and returning 
                        // it to callign function ... 
                        var response = {
                            object_info: {
                                publicURL: downloadUrl,
                                metainfo: meta
                            },
                            type_of_object: type
                        }
                        filehandle.fullPath = meta.fullPath
                        return cb(response)
                    })
                })

                // Hiding progress bar for current file 
                progressBar.style.opacity = 0
            }
        )

}