Image upload with AngularJS + Node.js + Firebase

file-upload.js

// Angular controller

$scope.imageUpload = function(event, index) {
    var files = event.target.files //FileList object

    for (var i = 0; i < files.length; i++) {
        var file = files[i]
        var reader = new FileReader()
        reader.onload = (function(index){
            return function(e) {
                $scope.$apply(function() {
                    self.picture = e.target.result // I'm uploading this variable that stores the encoded file (base64)
                })
            }
        })(index)
        reader.readAsDataURL(file)
    }
}

node-api.js

// Express route running on my Node api

const express = require('express')
const router = express.Router()
const admin = require('firebase-admin')
const stream = require('stream')

const MyMongoEntity = require('../../model/my-mongo-entity')

router.post('/resource', (req, res) => {
    if(!req.body.field1 || !req.body.field2 || !req.body.field3) {
        res.status(500).json({
            message: 'Malformed body',
            error: {
                status: 500
            }
        })
    } else {
        const bucket = admin.storage().bucket('my-awesome-project.appspot.com')

        let c = new MyMongoEntity(req.body)

        c.save(err => {
            if (err) { throw err }
            
            let fileB64 = req.body.band.split(';')
            let mime = fileB64[0].split(':')[1]

            if(!mime) fileB64[1] = mime = 'image/png'

            let decodedImage = new Buffer(fileB64[1].substring(7), 'base64')
            let bufferStream = new stream.PassThrough()
            bufferStream.end(decodedImage)

            let file = bucket.file(`my-resource/${c._id}/file.${mime.split('/')[1]}`)
        
            bufferStream
                .pipe(file.createWriteStream({
                    metadata: {
                        contentType: mime
                    } 
                }))
                .on('error', err => {
                    throw err
                })
                .on('finish', () => {
                    res.json(c)
                })
        })
    }
})