语言中间件

¥Language Middleware

语言检测器中间件会自动从各种来源确定用户的首选语言（语言环境），并通过 c.get('language') 提供该语言。检测策略包括查询参数、cookie、标头和 URL 路径段。非常适合国际化 (i18n) 和特定于语言环境的内容。

¥The Language Detector middleware automatically determines a user's preferred language (locale) from various sources and makes it available via c.get('language'). Detection strategies include query parameters, cookies, headers, and URL path segments. Perfect for internationalization (i18n) and locale-specific content.

导入

¥Import

import { Hono } from 'hono'
import { languageDetector } from 'hono/language'

基本用法

¥Basic Usage

从查询字符串、cookie 和标头（默认顺序）检测语言，并回退到英语：

¥Detect language from query string, cookie, and header (default order), with fallback to English:

const app = new Hono()

app.use(
  languageDetector({
    supportedLanguages: ['en', 'ar', 'ja'], // Must include fallback
    fallbackLanguage: 'en', // Required
  })
)

app.get('/', (c) => {
  const lang = c.get('language')
  return c.text(`Hello! Your language is ${lang}`)
})

客户端示例

¥Client Examples

# Via path
curl http://localhost:8787/ar/home

# Via query parameter
curl http://localhost:8787/?lang=ar

# Via cookie
curl -H 'Cookie: language=ja' http://localhost:8787/

# Via header
curl -H 'Accept-Language: ar,en;q=0.9' http://localhost:8787/

默认配置

¥Default Configuration

export const DEFAULT_OPTIONS: DetectorOptions = {
  order: ['querystring', 'cookie', 'header'],
  lookupQueryString: 'lang',
  lookupCookie: 'language',
  lookupFromHeaderKey: 'accept-language',
  lookupFromPathIndex: 0,
  caches: ['cookie'],
  ignoreCase: true,
  fallbackLanguage: 'en',
  supportedLanguages: ['en'],
  cookieOptions: {
    sameSite: 'Strict',
    secure: true,
    maxAge: 365 * 24 * 60 * 60,
    httpOnly: true,
  },
  debug: false,
}

关键行为

¥Key Behaviors

检测工作流程

¥Detection Workflow

1. 顺序：默认按此顺序检查源：

   ¥Order: Checks sources in this sequence by default:

   • 查询参数 (?lang=ar)

     ¥Query parameter (?lang=ar)

   • Cookie（语言=ar）

     ¥Cookie (language=ar)

   • Accept-Language 标头

     ¥Accept-Language header

2. 缓存:将检测到的语言存储在 cookie 中（默认为 1 年）

   ¥Caching: Stores detected language in a cookie (1 year by default)

3. 后备：如果没有有效检测则使用 fallbackLanguage（必须在 supportedLanguages 中）

   ¥Fallback: Uses fallbackLanguage if no valid detection (must be in supportedLanguages)

高级配置

¥Advanced Configuration

自定义检测顺序

¥Custom Detection Order

优先考虑 URL 路径检测（例如，/en/about）：

¥Prioritize URL path detection (e.g., /en/about):

app.use(
  languageDetector({
    order: ['path', 'cookie', 'querystring', 'header'],
    lookupFromPathIndex: 0, // /en/profile → index 0 = 'en'
    supportedLanguages: ['en', 'ar'],
    fallbackLanguage: 'en',
  })
)

语言代码转换

¥Language Code Transformation

规范化复杂代码（例如，en-US → en）：

¥Normalize complex codes (e.g., en-US → en):

app.use(
  languageDetector({
    convertDetectedLanguage: (lang) => lang.split('-')[0],
    supportedLanguages: ['en', 'ja'],
    fallbackLanguage: 'en',
  })
)

Cookie 配置

¥Cookie Configuration

app.use(
  languageDetector({
    lookupCookie: 'app_lang',
    caches: ['cookie'],
    cookieOptions: {
      path: '/', // Cookie path
      sameSite: 'Lax', // Cookie same-site policy
      secure: true, // Only send over HTTPS
      maxAge: 86400 * 365, // 1 year expiration
      httpOnly: true, // Not accessible via JavaScript
      domain: '.example.com', // Optional: specific domain
    },
  })
)

要禁用 cookie 缓存：

¥To disable cookie caching:

languageDetector({
  caches: false,
})

调试

¥Debugging

日志检测步骤：

¥Log detection steps:

languageDetector({
  debug: true, // Shows: "Detected from querystring: ar"
})

选项参考

¥Options Reference

基本选项

¥Basic Options

选项	类型	默认	必需	描述
supportedLanguages	string[]	['en']	是	允许的语言代码
fallbackLanguage	string	'en'	是	默认语言
order	DetectorType[]	['querystring', 'cookie', 'header']	否	检测序列
debug	boolean	false	否	启用日志记录

检测选项

¥Detection Options

选项	类型	默认	描述
lookupQueryString	string	'lang'	查询参数名称
lookupCookie	string	'language'	Cookie 名称
lookupFromHeaderKey	string	'accept-language'	标头名称
lookupFromPathIndex	number	0	路径段索引

Cookie 选项

¥Cookie Options

选项	类型	默认	描述
caches	CacheType[] | false	['cookie']	缓存设置
cookieOptions.path	string	'/'	Cookie 路径
cookieOptions.sameSite	'Strict' | 'Lax' | 'None'	'Strict'	SameSite 策略
cookieOptions.secure	boolean	true	仅 HTTPS
cookieOptions.maxAge	number	31536000	到期时间（秒）
cookieOptions.httpOnly	boolean	true	JS 可访问性
cookieOptions.domain	string	undefined	Cookie 域

高级选项

¥Advanced Options

选项	类型	默认	描述
ignoreCase	boolean	true	不区分大小写的匹配
convertDetectedLanguage	(lang: string) => string	undefined	语言代码转换器

验证和错误处理

¥Validation & Error Handling

• fallbackLanguage 必须在 supportedLanguages 中（设置期间会抛出错误）

  ¥fallbackLanguage must be in supportedLanguages (throws error during setup)

• lookupFromPathIndex 必须≥0

  ¥lookupFromPathIndex must be ≥ 0

• 无效配置在中间件初始化期间抛出错误

  ¥Invalid configurations throw errors during middleware initialization

• 失败的检测会默默使用 fallbackLanguage

  ¥Failed detections silently use fallbackLanguage

常用秘诀

¥Common Recipes

基于路径的路由

¥Path-Based Routing

app.get('/:lang/home', (c) => {
  const lang = c.get('language') // 'en', 'ar', etc.
  return c.json({ message: getLocalizedContent(lang) })
})

支持多种语言

¥Multiple Supported Languages

languageDetector({
  supportedLanguages: ['en', 'en-GB', 'ar', 'ar-EG'],
  convertDetectedLanguage: (lang) => lang.replace('_', '-'), // Normalize
})