separated file into upload and download files, changed single quotes to double quotes, added progress indicator

public/upload.js

@@ -0,0 +1,88 @@
+function onChange(event) {
+  var file = event.target.files[0];
+  var reader = new FileReader();
+  reader.onload = function(event) {
+    let self = this;
+    window.crypto.subtle.generateKey({
+      name: "AES-CBC",
+      length: 128 
+    },
+    true,
+    ["encrypt", "decrypt"])
+    .then(function(key){
+      var arrayBuffer = self.result;
+      var array = new Uint8Array(arrayBuffer);
+
+      var random_iv = window.crypto.getRandomValues(new Uint8Array(16));
+
+      window.crypto.subtle.encrypt({
+        name: "AES-CBC",
+        iv: random_iv },
+        key,
+        array)
+        .then(function(encrypted){
+          var dataView = new DataView(encrypted);
+          var blob = new Blob([dataView], { type: file.type });
+          
+          var fd = new FormData();
+          fd.append("fname", file.name);
+          fd.append("data", blob, file.name);
+
+          var xhr = new XMLHttpRequest();
+          var hex = ivToStr(random_iv);
+          xhr.open("post", "/upload/" + hex, true);
+          xhr.addEventListener("progress", updateProgress);
+          xhr.upload.addEventListener("progress", updateProgress);
+
+          xhr.onreadystatechange = function() { 
+            if (xhr.readyState == XMLHttpRequest.DONE) {
+              window.crypto.subtle.exportKey("jwk", key).then(function(keydata) {
+                console.log("Share this link with a friend: http://localhost:3000/download/" + hex + "/#" + keydata.k);
+                alert("Share this link with a friend: http://localhost:3000/download/" + hex + "/#" + keydata.k);
+              })
+            }
+          };
+
+          xhr.send(fd);
+        })
+        .catch(function(err){
+          console.error(err);
+        });
+
+      })
+    .catch(function(err){
+        console.error(err);
+    });
+    
+  };
+  reader.readAsArrayBuffer(file);
+}
+
+function ivToStr(iv) {
+  let hexStr = "";
+  for (var i in iv) {
+    if (iv[i] < 16) {
+      hexStr += "0" + iv[i].toString(16);
+    } else {
+      hexStr += iv[i].toString(16);
+    }
+  }
+  window.hexStr = hexStr;
+  return hexStr;
+}
+
+function strToIv(str) {
+  var iv = new Uint8Array(16);
+  for (var i = 0; i < str.length; i += 2) {
+    iv[i/2] = parseInt((str.charAt(i) + str.charAt(i + 1)), 16);
+  }
+
+  return iv;
+}
+
+function updateProgress(e) {
+  if (e.lengthComputable) { 
+    var percentComplete = Math.floor((e.loaded / e.total) * 100);
+    document.getElementById("downloadProgress").innerHTML = "Progress: " + percentComplete + "%";
+  } 
+}