feat: Improve performance of Uint8Array Hex functions (#1510)

johnzhou721 · zloirock · web-flow · commit 28cf2e9b16f4 · 2026-02-28T18:20:58.000+07:00
* feat: Improve performance of Uint8Array Hex functions

* Typo fix

* op prec

* Update uint8-from-hex.js

* Update uint8-from-hex.js

* Update uint8-from-hex.js

* Fix

* Improvements

* Lint

* Lint, cl

* Requested Changes.

* Cache min

* Fix tests

* some fixes

---------

Co-authored-by: Denis Pushkarev &lt;zloirock@zloirock.ru&gt;
diff --git a/CHANGELOG.md b/CHANGELOG.md
@@ -1,6 +1,6 @@
 # Changelog
 ### Unreleased
-- Improved performance of `atob` and `btoa`, [#1503](https://github.com/zloirock/core-js/issues/1503), [#1464](https://github.com/zloirock/core-js/issues/1464)
+- Improved performance of `atob`, `btoa`, `Uint8Array.fromHex`, `Uint8Array.prototype.setFromHex`, and `Uint8Array.prototype.toHex`, [#1503](https://github.com/zloirock/core-js/issues/1503), [#1464](https://github.com/zloirock/core-js/issues/1464), [#1510](https://github.com/zloirock/core-js/issues/1510)
 - [`Iterator.range`](https://github.com/tc39/proposal-iterator.range) updated following the actual spec version
   - Throw a `RangeError` on `NaN` `start` / `end` / `step`
   - Allow `null` as `optionOrStep`
diff --git a/packages/core-js/internals/uint8-from-hex.js b/packages/core-js/internals/uint8-from-hex.js
@@ -4,23 +4,24 @@ var uncurryThis = require('../internals/function-uncurry-this');
 
 var Uint8Array = globalThis.Uint8Array;
 var SyntaxError = globalThis.SyntaxError;
-var parseInt = globalThis.parseInt;
 var min = Math.min;
-var NOT_HEX = /[^\da-f]/i;
-var exec = uncurryThis(NOT_HEX.exec);
-var stringSlice = uncurryThis(''.slice);
+var stringMatch = uncurryThis(''.match);
 
 module.exports = function (string, into) {
   var stringLength = string.length;
   if (stringLength % 2 !== 0) throw new SyntaxError('String should be an even number of characters');
   var maxLength = into ? min(into.length, stringLength / 2) : stringLength / 2;
   var bytes = into || new Uint8Array(maxLength);
-  var read = 0;
+  // This splitting is faster than using substrings each time.
+  var segments = stringMatch(string, /.{2}/g);
   var written = 0;
-  while (written < maxLength) {
-    var hexits = stringSlice(string, read, read += 2);
-    if (exec(NOT_HEX, hexits)) throw new SyntaxError('String should only contain hex characters');
-    bytes[written++] = parseInt(hexits, 16);
+  for (; written < maxLength; written++) {
+    var result = +('0x' + segments[written] + '0');
+    // eslint-disable-next-line no-self-compare -- NaN check
+    if (result !== result) {
+      throw new SyntaxError('String should only contain hex characters');
+    }
+    bytes[written] = result >> 4;
   }
-  return { bytes: bytes, read: read };
+  return { bytes: bytes, read: written << 1 };
 };
diff --git a/packages/core-js/modules/es.uint8-array.to-hex.js b/packages/core-js/modules/es.uint8-array.to-hex.js
@@ -6,6 +6,8 @@ var anUint8Array = require('../internals/an-uint8-array');
 var notDetached = require('../internals/array-buffer-not-detached');
 
 var numberToString = uncurryThis(1.1.toString);
+var join = uncurryThis([].join);
+var $Array = Array;
 
 var Uint8Array = globalThis.Uint8Array;
 
@@ -24,11 +26,11 @@ if (Uint8Array) $({ target: 'Uint8Array', proto: true, forced: INCORRECT_BEHAVIO
   toHex: function toHex() {
     anUint8Array(this);
     notDetached(this.buffer);
-    var result = '';
+    var result = $Array(this.length);
     for (var i = 0, length = this.length; i < length; i++) {
       var hex = numberToString(this[i], 16);
-      result += hex.length === 1 ? '0' + hex : hex;
+      result[i] = hex.length === 1 ? '0' + hex : hex;
     }
-    return result;
+    return join(result, '');
   }
 });
diff --git a/tests/unit-global/es.uint8-array.set-from-hex.js b/tests/unit-global/es.uint8-array.set-from-hex.js
@@ -37,6 +37,15 @@ if (DESCRIPTORS) QUnit.test('Uint8Array.prototype.setFromHex', assert => {
     assert.throws(() => array5.setFromHex('48656c6c6f20576f726c64'), TypeError, 'detached');
   }
 
+  // Should not throw an error with an empty string being set.  This verifies that
+  // we aren't using the result of segments = stringMatch(string, /.{2}/g) unsafely
+  // in cases where no matches are found, since it returns null instead of []
+  const arrayEmpty = new Uint8Array(4);
+  const resultEmpty = arrayEmpty.setFromHex('');
+
+  assert.deepEqual(arrayEmpty, new Uint8Array([0, 0, 0, 0]), 'array empty string test');
+  assert.deepEqual(resultEmpty, { read: 0, written: 0 }, 'result empty string test');
+
   // Should not throw an error on length-tracking views over ResizableArrayBuffer
   // https://issues.chromium.org/issues/454630441
   assert.notThrows(() => {
