lib: use primordials for navigator.userAgent

PR-URL: #50467
Reviewed-By: Geoffrey Booth <webadmin@geoffreybooth.com>
Reviewed-By: Vinícius Lourenço Claro Cardoso <contact@viniciusl.com.br>
Reviewed-By: Yagiz Nizipli <yagiz@nizipli.com>
Reviewed-By: James M Snell <jasnell@gmail.com>
Reviewed-By: Tobias Nießen <tniessen@tnie.de>
Reviewed-By: Ethan Arrowood <ethan@arrowood.dev>

lib/internal/navigator.js

@@ -0,0 +1,61 @@
+'use strict';
+
+const {
+  ObjectDefineProperties,
+  StringPrototypeIndexOf,
+  StringPrototypeSlice,
+  Symbol,
+} = primordials;
+
+const {
+  ERR_ILLEGAL_CONSTRUCTOR,
+} = require('internal/errors').codes;
+
+const {
+  kEnumerableProperty,
+} = require('internal/util');
+
+const {
+  getAvailableParallelism,
+} = internalBinding('os');
+
+const kInitialize = Symbol('kInitialize');
+const nodeVersion = process.version;
+
+class Navigator {
+  // Private properties are used to avoid brand validations.
+  #availableParallelism;
+  #userAgent = `Node.js/${StringPrototypeSlice(nodeVersion, 1, StringPrototypeIndexOf(nodeVersion, '.'))}`;
+
+  constructor() {
+    if (arguments[0] === kInitialize) {
+      return;
+    }
+    throw new ERR_ILLEGAL_CONSTRUCTOR();
+  }
+
+  /**
+   * @return {number}
+   */
+  get hardwareConcurrency() {
+    this.#availableParallelism ??= getAvailableParallelism();
+    return this.#availableParallelism;
+  }
+
+  /**
+   * @return {string}
+   */
+  get userAgent() {
+    return this.#userAgent;
+  }
+}
+
+ObjectDefineProperties(Navigator.prototype, {
+  hardwareConcurrency: kEnumerableProperty,
+  userAgent: kEnumerableProperty,
+});
+
+module.exports = {
+  navigator: new Navigator(kInitialize),
+  Navigator,
+};