detectFromHeader

Kind: Function

Source: src/middleware/language/language.ts

Part of: Middleware

Detects language from Accept-Language header

detectFromHeader reads the Accept-Language header and determines the requested language. It is used by language middleware to select a language before handling a request.

Signature

ts
function detectFromHeader(c: Context, options: DetectorOptions): string | undefined

Parameters

Returns: string | undefined

Diagram

mermaid
graph LR
  Request[Incoming request] --> Header[Accept-Language header]
  Header --> Detect[detectFromHeader]
  Detect --> Language[Detected language]
  Language --> Middleware[Language middleware]

Usage

ts
import { detectFromHeader } from './middleware/language/language';

const language = detectFromHeader('fr-CA,fr,en');

if (language) {
  console.log(`Detected language: ${language}`);
}

AI Coding Instructions

• Pass the raw Accept-Language header value to detectFromHeader.
• Handle an absent or unmatched language result before setting request language state.
• Keep header parsing in this function rather than duplicating parsing logic in middleware handlers.