feat: add getQueryLanguage and getQueryLocale

README.md

@@ -146,6 +146,8 @@ You can do `import { ... } from '@intlify/utils'` the above utilities
 - `setCookieLocale`
 - `getPathLanguage`
 - `getPathLocale`
+- `getQueryLanguage`
+- `getQueryLocale`
 
 The about utilies functions accpet Web APIs such as
 [Request](https://developer.mozilla.org/en-US/docs/Web/API/Request) and

src/http.test.ts

@@ -1,5 +1,10 @@
 import { describe, expect, test } from 'vitest'
-import { getPathLanguage, getPathLocale } from './http.ts'
+import {
+  getPathLanguage,
+  getPathLocale,
+  getQueryLanguage,
+  getQueryLocale,
+} from './http.ts'
 
 describe('getPathLanguage', () => {
   test('basic', () => {
@@ -38,3 +43,47 @@ describe('getPathLocale', () => {
     )
   })
 })
+
+describe('getQueryLanguage', () => {
+  test('basic', () => {
+    expect(getQueryLanguage('lang=en-US&flag=1')).toBe('en-US')
+  })
+
+  test('URL instance', () => {
+    const url = new URL('https://example.com/?locale=ja-JP')
+    expect(getQueryLanguage(url, 'locale')).toBe('ja-JP')
+  })
+
+  test('URLSearchParams instance', () => {
+    const params = new URLSearchParams('lang=ja-JP')
+    params.set('flag', '1')
+    expect(getQueryLanguage(params)).toBe('ja-JP')
+  })
+
+  test('empty', () => {
+    const params = new URLSearchParams()
+    expect(getQueryLanguage(params)).toBe('')
+  })
+})
+
+describe('getQueryLocale', () => {
+  test('basic', () => {
+    expect(getQueryLocale('lang=en-US&flag=1', 'lang').toString()).toBe('en-US')
+  })
+
+  test('URL instance', () => {
+    const url = new URL('https://example.com/?locale=ja-JP')
+    expect(getQueryLocale(url).toString()).toBe('ja-JP')
+  })
+
+  test('URLSearchParams instance', () => {
+    const params = new URLSearchParams('lang=ja-JP')
+    params.set('flag', '1')
+    expect(getQueryLocale(params, 'lang').toString()).toBe('ja-JP')
+  })
+
+  test('RangeError', () => {
+    const params = new URLSearchParams()
+    expect(() => getQueryLocale(params)).toThrowError(RangeError)
+  })
+})

src/http.ts

@@ -1,5 +1,7 @@
 import {
   isLocale,
+  isURL,
+  isURLSearchParams,
   parseAcceptLanguage,
   pathLanguageParser,
   validateLanguageTag,
@@ -158,7 +160,7 @@ export function getExistCookies(
  * @param {string | URL} path the target path
  * @param {PathLanguageParser} parser the path language parser, optional
  *
- * @returns {string} the language that is parsed by the path language parser
+ * @returns {string} the language that is parsed by the path language parser, if the language is not detected, return an empty string.
  */
 export function getPathLanguage(
   path: string | URL,
@@ -184,3 +186,48 @@ export function getPathLocale(
 ): Intl.Locale {
   return new Intl.Locale(getPathLanguage(path, parser))
 }
+
+function getURLSearchParams(
+  input: string | URL | URLSearchParams,
+): URLSearchParams {
+  if (isURLSearchParams(input)) {
+    return input
+  } else if (isURL(input)) {
+    return input.searchParams
+  } else {
+    return new URLSearchParams(input)
+  }
+}
+
+/**
+ * get the language from the query
+ *
+ * @param {string | URL | URLSearchParams} query the target query
+ * @param {string} name the query param name, default `'lang'`
+ *
+ * @returns {string} the language from query, if the language is not detected, return an empty string.
+ */
+export function getQueryLanguage(
+  query: string | URL | URLSearchParams,
+  name = 'lang',
+): string {
+  const queryParams = getURLSearchParams(query)
+  return queryParams.get(name) || ''
+}
+
+/**
+ * get the locale from the query
+ *
+ * @param {string | URL | URLSearchParams} query the target query
+ * @param {string} name the query param name, default `'locale'`
+ *
+ * @throws {RangeError} Throws the {@link RangeError} if the language in the query, that is not a well-formed BCP 47 language tag.
+ *
+ * @returns {Intl.Locale} The locale that resolved from query
+ */
+export function getQueryLocale(
+  query: string | URL | URLSearchParams,
+  name = 'locale',
+): Intl.Locale {
+  return new Intl.Locale(getQueryLanguage(query, name))
+}

src/index.ts

@@ -6,5 +6,10 @@ export {
   registerPathLanguageParser,
   validateLanguageTag,
 } from './shared.ts'
-export { getPathLanguage, getPathLocale } from './http.ts'
+export {
+  getPathLanguage,
+  getPathLocale,
+  getQueryLanguage,
+  getQueryLocale,
+} from './http.ts'
 export * from './web.ts'

src/shared.ts

@@ -1,6 +1,14 @@
 const objectToString = Object.prototype.toString
 const toTypeString = (value: unknown): string => objectToString.call(value)
 
+export function isURL(val: unknown): val is URL {
+  return toTypeString(val) === '[object URL]'
+}
+
+export function isURLSearchParams(val: unknown): val is URLSearchParams {
+  return toTypeString(val) === '[object URLSearchParams]'
+}
+
 /**
  * check whether the value is a {@link Intl.Locale} instance
  *