video: Getting Started with Firebase Storage on the Web - Firecasts

  <progress value="0" max="100" id="uploader"></progress>
<input type="file" value="upload" id="fileButton" />

  var uploader = document.getElementById('uploader')
var fileButton = document.getElementById('fileButton')


fileButton.addEventListener('change', function (e) {
  // Get file
  var file = e.target.files[0]
  
  // Create a storage ref
  var storageRef = firebase.storage().ref('sweet_gifs/' + file.name)
  
  // Upload file
  var task = storageRef.put(file)
  
  // Update progress bar
  task.on('state_changed', 
    function progress(snapshot) {
      var percentage = (snapshot.bytesTrasferred / snapshot.totalBytes) * 100
      uploader.value = percentage
      
    },
    function error(err) {
      
    },
    function complete() {
      
    }
  )
  
  
})