Firebase Storage: What It Is and How It Works

MonitorProgresswithTasks.js

var storageRef = firebase.storage.ref("folderName/file.jpg");

var fileUpload = document.getElementById("fileUpload");

fileUpload.on('change', function(evt) {

  var firstFile = evt.target.file[0]; 

  var uploadTask = storageRef.put(firstFile);

  uploadTask.on('state_changed', function progress(snapshot) {

     console.log(snapshot.totalBytesTransferred); 

  });

}