fix: mem issue when generating uuid (#267)

* fixed mem issues when generating uuid

* updated comment on memory issue

lib/bytesToUuid.js

@@ -10,14 +10,15 @@ for (var i = 0; i < 256; ++i) {
 function bytesToUuid(buf, offset) {
   var i = offset || 0;
   var bth = byteToHex;
-  return bth[buf[i++]] + bth[buf[i++]] +
-          bth[buf[i++]] + bth[buf[i++]] + '-' +
-          bth[buf[i++]] + bth[buf[i++]] + '-' +
-          bth[buf[i++]] + bth[buf[i++]] + '-' +
-          bth[buf[i++]] + bth[buf[i++]] + '-' +
-          bth[buf[i++]] + bth[buf[i++]] +
-          bth[buf[i++]] + bth[buf[i++]] +
-          bth[buf[i++]] + bth[buf[i++]];
+  // join used to fix memory issue caused by concatenation: https://bugs.chromium.org/p/v8/issues/detail?id=3175#c4
+  return ([bth[buf[i++]], bth[buf[i++]], 
+	bth[buf[i++]], bth[buf[i++]], '-',
+	bth[buf[i++]], bth[buf[i++]], '-',
+	bth[buf[i++]], bth[buf[i++]], '-',
+	bth[buf[i++]], bth[buf[i++]], '-',
+	bth[buf[i++]], bth[buf[i++]],
+	bth[buf[i++]], bth[buf[i++]],
+	bth[buf[i++]], bth[buf[i++]]]).join('');
 }
 
 module.exports = bytesToUuid;