lib: add navigator.language & navigator.languages

doc/api/globals.md

@@ -637,6 +637,41 @@ logical processors available to the current Node.js instance.
 console.log(`This process is running on ${navigator.hardwareConcurrency} logical processors`);
 ```
 
+
+### `navigator.language`
+
+<!-- YAML
+added: REPLACEME
+-->
+
+* {string}
+
+The `navigator.language` read-only property returns a string representing the
+preferred language of the Node.js instance.
+
+The value is representing the language version as defined in RFC <5646>.
+The default value is `'en-US'`.
+
+```js
+console.log(`The preferred language of the Node.js instance has the tag '${navigator.language}'`);
+```
+
+### `navigator.languages`
+
+<!-- YAML
+added: REPLACEME
+-->
+
+* {Array<string>}
+
+The `navigator.languages` read-only property returns an array of strings
+representing the preferred languages of the Node.js instance.
+The default value is `['en-US']`.
+
+```js
+console.log(`The preferred languages are '${navigator.language}'`);
+```
+
 ### `navigator.userAgent`
 
 <!-- YAML

lib/internal/navigator.js

@@ -2,6 +2,7 @@
 
 const {
   ObjectDefineProperties,
+  ObjectFreeze,
   Symbol,
 } = primordials;
 
@@ -40,6 +41,20 @@ class Navigator {
     return this.#availableParallelism;
   }
 
+  /**
+   * @return {string}
+   */
+  get language() {
+    return 'en-US';
+  }
+
+  /**
+   * @return {Array<string>}
+   */
+  get languages() {
+    return ObjectFreeze([this.language]);
+  }
+
   /**
    * @return {string}
    */

test/parallel/test-navigator.js

@@ -15,3 +15,19 @@ is.number(navigator.hardwareConcurrency, 'hardwareConcurrency');
 assert.ok(navigator.hardwareConcurrency > 0);
 assert.strictEqual(typeof navigator.userAgent, 'string');
 assert.match(navigator.userAgent, /^Node\.js\/\d+$/);
+
+assert.strictEqual(typeof navigator.language, 'string');
+assert.strictEqual(navigator.language, 'en-US');
+
+assert.ok(Array.isArray(navigator.languages));
+assert.strictEqual(navigator.languages.length, 1);
+assert.strictEqual(typeof navigator.languages[0], 'string');
+
+assert.throws(() => {navigator.languages[0] = 'foo'}, new TypeError("Cannot assign to read only property '0' of object '[object Array]'"));
+assert.notStrictEqual(navigator.languages[0], 'foo');
+assert.strictEqual(navigator.languages[0], 'en-US');
+
+Object.defineProperty(navigator, 'language', {value: 'de-DE'});
+assert.strictEqual(navigator.language, 'de-DE');
+assert.strictEqual(navigator.languages.length, 1);
+assert.strictEqual(navigator.languages[0], 'de-DE');