normalizeLanguage

Kind: Function

Source: src/middleware/language/language.ts

Part of: Middleware

Validate and normalize language codes

normalizeLanguage validates an incoming language code and converts it to the format expected by the language middleware. It acts as a boundary between external request values and the normalized language value used by the application.

Signature

ts
function normalizeLanguage(lang: string | null | undefined, options: DetectorOptions): string | undefined

Parameters

Returns: string | undefined

Diagram

mermaid
graph LR
  A[Incoming language code] --> B[normalizeLanguage]
  B --> C{Valid code?}
  C -->|Yes| D[Normalized language code]
  C -->|No| E[Fallback or validation result]

Usage

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

const requestedLanguage = 'EN-us';
const language = normalizeLanguage(requestedLanguage);

console.log(language);

AI Coding Instructions

• Pass request-derived language values through normalizeLanguage before using them for locale selection or translations.
• Keep language-code formatting rules in this function rather than duplicating case conversion or validation in middleware callers.
• Preserve the function’s handling of invalid or missing values when changing language middleware behavior.
• Update callers and tests together if supported language codes or fallback behavior changes.