lib: add navigator.language & navigator.languages

Author: Uzlopak

doc/api/globals.md

@@ -637,6 +637,51 @@ 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][].
+
+You can override the value of `navigator.language` by setting the
+`LC_ALL` environment variable.
+
+For example:
+
+```sh
+LC_ALL=fr-FR node -p "console.log(navigator.language)"
+```
+
+The fallback value on builds without ICU is `'en-US'`.
+
+```js
+console.log(`The preferred language of the Node.js instance has the tag '${navigator.language}'`);
+```
+
+### `navigator.languages`
+
+<!-- YAML
+added: REPLACEME
+-->
+
+*{Array<string>}
+
+The `navigator.languages` read-only property returns an array of strings
+representing the preferred languages of the Node.js instance.
+By default it contains only the value of `navigator.language`.
+The fallback value on builds without ICU is `['en-US']`.
+
+```js
+console.log(`The preferred languages are '${navigator.language}'`);
+```
+
 ### `navigator.userAgent`
 
 <!-- YAML
@@ -1085,6 +1130,7 @@ A browser-compatible implementation of [`WritableStreamDefaultWriter`][].
 [CommonJS module]: modules.md
 [ECMAScript module]: esm.md
 [Navigator API]: https://html.spec.whatwg.org/multipage/system-state.html#the-navigator-object
+[RFC 5646]: https://www.rfc-editor.org/rfc/rfc5646.txt
 [Web Crypto API]: webcrypto.md
 [`--experimental-websocket`]: cli.md#--experimental-websocket
 [`--no-experimental-global-customevent`]: cli.md#--no-experimental-global-customevent

lib/internal/navigator.js

@@ -2,9 +2,15 @@
 
 const{
  ObjectDefineProperties,
+ ObjectFreeze,
+ globalThis,
  Symbol,
 }=primordials;
 
+const{
+ Intl,
+}=globalThis;
+
 const{
 ERR_ILLEGAL_CONSTRUCTOR,
 }=require('internal/errors').codes;
@@ -24,6 +30,8 @@ class Navigator{
 // Private properties are used to avoid brand validations.
  #availableParallelism;
  #userAgent =`Node.js/${nodeVersion.slice(1,nodeVersion.indexOf('.'))}`;
+ #language =Intl?.Collator().resolvedOptions().locale||'en-US';
+ #languages =ObjectFreeze([this.#language]);
 
 constructor(){
 if(arguments[0]===kInitialize){
@@ -40,6 +48,20 @@ class Navigator{
 returnthis.#availableParallelism;
 }
 
+/**
+ * @return{string}
+ */
+getlanguage(){
+returnthis.#language;
+}
+
+/**
+ * @return{Array<string>}
+ */
+getlanguages(){
+returnthis.#languages;
+}
+
 /**
  * @return{string}
  */
@@ -50,6 +72,8 @@ class Navigator{
 
 ObjectDefineProperties(Navigator.prototype,{
 hardwareConcurrency: kEnumerableProperty,
+language: kEnumerableProperty,
+languages: kEnumerableProperty,
 userAgent: kEnumerableProperty,
 });
 

test/parallel/test-navigator.js

@@ -1,7 +1,8 @@
 'use strict';
 
-require('../common');
+constcommon=require('../common');
 constassert=require('assert');
+const{ execFile }=require('child_process');
 
 constis={
 number: (value,key)=>{
@@ -15,3 +16,44 @@ is.number(navigator.hardwareConcurrency, 'hardwareConcurrency');
 assert.ok(navigator.hardwareConcurrency>0);
 assert.strictEqual(typeofnavigator.userAgent,'string');
 assert.match(navigator.userAgent,/^Node\.js\/\d+$/);
+
+assert.strictEqual(typeofnavigator.language,'string');
+assert.strictEqual(navigator.language,'en-US');
+
+assert.ok(Array.isArray(navigator.languages));
+assert.strictEqual(navigator.languages.length,1);
+assert.strictEqual(typeofnavigator.languages[0],'string');
+
+assert.throws(()=>{
+navigator.languages[0]='foo';
+},newTypeError("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],'en-US');
+
+
+if(common.hasIntl){
+{
+constenv={ ...process.env,LC_ALL: 'fr-FR'};
+execFile(
+process.execPath,
+['-p','process.exit(navigator.language === "fr-FR" ? 0 : 1)'],
+{ env },
+common.mustSucceed()
+);
+}
+
+{
+constenv={ ...process.env,LC_ALL: 'fr-FR'};
+execFile(
+process.execPath,
+['-p','process.exit(navigator.languages[0] === "fr-FR" ? 0 : 1)'],
+{ env },
+common.mustSucceed()
+);
+}
+}