feat: optimize V8 performance of bytesToUuid (#434)

Author: awwit

examples/benchmark/benchmark.js

@@ -9,7 +9,12 @@ const uuidv5 = (typeof window !== 'undefined' && window.uuidv5) || require('uuid
 console.log('Starting. Tests take ~1 minute to run ...');
 
 const array = new Array(16);
-const suite = new Benchmark.Suite();
+
+const suite = new Benchmark.Suite({
+  onError(event) {
+    console.error(event.target.error);
+  },
+});
 
 suite
   .add('uuidv1()', function () {

src/bytesToUuid.js

@@ -13,29 +13,30 @@ function bytesToUuid(buf, offset) {
 
   const bth = byteToHex;
 
-  // join used to fix memory issue caused by concatenation: https://bugs.chromium.org/p/v8/issues/detail?id=3175#c4
-  return [
-    bth[buf[i + 0]],
-    bth[buf[i + 1]],
-    bth[buf[i + 2]],
-    bth[buf[i + 3]],
-    '-',
-    bth[buf[i + 4]],
-    bth[buf[i + 5]],
-    '-',
-    bth[buf[i + 6]],
-    bth[buf[i + 7]],
-    '-',
-    bth[buf[i + 8]],
-    bth[buf[i + 9]],
-    '-',
-    bth[buf[i + 10]],
-    bth[buf[i + 11]],
-    bth[buf[i + 12]],
-    bth[buf[i + 13]],
-    bth[buf[i + 14]],
-    bth[buf[i + 15]],
-  ].join('');
+  // Note: Be careful editing this code!  It's been tuned for performance
+  // and works in ways you may not expect. See https://github.com/uuidjs/uuid/pull/434
+  return (
+    bth[buf[i + 0]] +
+    bth[buf[i + 1]] +
+    bth[buf[i + 2]] +
+    bth[buf[i + 3]] +
+    '-' +
+    bth[buf[i + 4]] +
+    bth[buf[i + 5]] +
+    '-' +
+    bth[buf[i + 6]] +
+    bth[buf[i + 7]] +
+    '-' +
+    bth[buf[i + 8]] +
+    bth[buf[i + 9]] +
+    '-' +
+    bth[buf[i + 10]] +
+    bth[buf[i + 11]] +
+    bth[buf[i + 12]] +
+    bth[buf[i + 13]] +
+    bth[buf[i + 14]] +
+    bth[buf[i + 15]]
+  ).toLowerCase();
 }
 
 export default bytesToUuid;