Fix IE11 memory leak

Author: adm90

lib/utils.js

@@ -1,4 +1,4 @@
-'use strict';
+'use strict';
 
 var support = require('./support');
 var base64 = require('./base64');
@@ -36,6 +36,29 @@ exports.newBlob = function(parts, type) {
     exports.checkSupport("blob");
 
     try {
+        // Fixed a memory leak occurred in IE11
+        // Note:
+        //    When a large amount of Array is generated in the Blob,
+        //    the amount of memory nearly 100 times the original data amount is consumed.
+        //    Change it to create a BLOB only once after join.
+        if (window.MSBlobBuilder) {
+            var concatenation = function(segments) {
+                var sumLength = 0;
+                for (var i = 0; i < segments.length; ++i) {
+                    sumLength += segments[i].byteLength;
+                }
+                var whole = new Uint8Array(sumLength);
+                var pos = 0;
+                for (var j = 0; j < segments.length; ++j) {
+                    whole.set(new Uint8Array(segments[j]), pos);
+                    pos += segments[j].byteLength;
+                }
+                return whole.buffer;
+            };
+            // array
+            parts = [concatenation(parts)];
+        }
+ 
         // Blob constructor
         return new Blob(parts, {
             type: type