Creation:2025-11-16Last update:2025-11-16

Reference this doc to your favorite AI assistantChatGPT Claude DeepSeek Google AI mode Gemini Perplexity Mistral Grok

Ask your question and get a summary of the document by referencing this page and the AI provider of your choice

Add the MCP Server to your AI Assistant

By integrating the Intlayer MCP Server to your favourite AI assistant can retrieve all the doc directly from ChatGPT, DeepSeek, Cursor, VSCode, etc.

See MCP Server doc

Version History

Initial documentation
v7.1.016/11/2025

The content of this page was translated using an AI.

See the last version of the original content in English

Edit this doc

If you have an idea for improving this documentation, please feel free to contribute by submitting a pull request on GitHub.

GitHub link to the documentation

Copy

Copy doc Markdown to clipboard

Documentation: getPrefix Function in intlayer

Description

The getPrefix function determines the URL prefix for a given locale based on the routing mode configuration. It compares the locale with the default locale and returns an object containing three different prefix formats for flexible URL construction.

Key Features:

Takes a locale as the first parameter (required)
Optional options object with defaultLocale and mode
Returns an object with prefix, and localePrefix properties
Supports all routing modes: prefix-no-default, prefix-all, no-prefix, and search-params
Lightweight utility for determining when to add locale prefixes

Function Signature

getPrefix(  locale: Locales,               // Required  options?: {                    // Optional    defaultLocale?: Locales;    mode?: 'prefix-no-default' | 'prefix-all' | 'no-prefix' | 'search-params';  }): GetPrefixResulttype GetPrefixResult = {  prefix: string;   // e.g., 'fr/' or ''  localePrefix?: Locale; // e.g., 'fr' or undefined}

getPrefix(  locale: Locales,               // Required  options?: {                    // Optional    defaultLocale?: Locales;    mode?: 'prefix-no-default' | 'prefix-all' | 'no-prefix' | 'search-params';  }): GetPrefixResulttype GetPrefixResult = {  prefix: string;   // e.g., 'fr/' or ''  localePrefix?: Locale; // e.g., 'fr' or undefined}

Parameters

locale: Locales
- Description: The locale to generate the prefix for. If the value is falsy (undefined, null, empty string), the function returns an empty string.
- Type: Locales
- Required: Yes
options?: object
- Description: Configuration object for prefix determination.
- Type: object
- Required: No (Optional)
- options.defaultLocale?: Locales
  - Description: The default locale for the application. If not provided, uses the configured default locale from your project configuration.
  - Type: Locales
  - Default: Project Configuration
- options.mode?: 'prefix-no-default' | 'prefix-all' | 'no-prefix' | 'search-params'
  - Description: The URL routing mode for locale handling. If not provided, uses the configured mode from your project configuration.
  - Type: 'prefix-no-default' | 'prefix-all' | 'no-prefix' | 'search-params'
  - Default: Project Configuration
  - Modes:
    - prefix-no-default: Returns empty strings when locale matches default locale
    - prefix-all: Returns prefix for all locales including default
    - no-prefix: Returns empty strings (no prefix in URLs)
    - search-params: Returns empty strings (locale in query parameters)

Returns

Type: GetPrefixResult
Description: An object containing three different prefix formats:
- prefix: The path prefix with trailing slash (e.g., 'fr/', '')
- localePrefix: The locale identifier without slashes (e.g., 'fr', undefined)

Example Usage

Basic Usage

import { getPrefix, Locales } from "intlayer";// Check prefix for English localegetPrefix(Locales.ENGLISH, {  defaultLocale: Locales.ENGLISH,  mode: "prefix-all",});// Returns: { prefix: 'en/', localePrefix: 'en' }// Check prefix for French localegetPrefix(Locales.FRENCH, {  defaultLocale: Locales.ENGLISH,  mode: "prefix-no-default",});// Returns: { prefix: 'fr/', localePrefix: 'fr' }

import { getPrefix, Locales } from "intlayer";// Check prefix for English localegetPrefix(Locales.ENGLISH, {  defaultLocale: Locales.ENGLISH,  mode: "prefix-all",});// Returns: { prefix: 'en/', localePrefix: 'en' }// Check prefix for French localegetPrefix(Locales.FRENCH, {  defaultLocale: Locales.ENGLISH,  mode: "prefix-no-default",});// Returns: { prefix: 'fr/', localePrefix: 'fr' }

Different Routing Modes

import { getPrefix, Locales } from "intlayer";// prefix-all: Always returns prefixgetPrefix(Locales.ENGLISH, {  mode: "prefix-all",  defaultLocale: Locales.ENGLISH,});// Returns: { prefix: '/en', localePrefix: 'en' }// prefix-no-default: No prefix when locale matches defaultgetPrefix(Locales.ENGLISH, {  mode: "prefix-no-default",  defaultLocale: Locales.ENGLISH,});// Returns: { prefix: '', localePrefix: undefined }// prefix-no-default: Returns prefix when locale differs from defaultgetPrefix(Locales.FRENCH, {  mode: "prefix-no-default",  defaultLocale: Locales.ENGLISH,});// Returns: { prefix: 'fr/', localePrefix: 'fr' }// no-prefix & search-params: Never returns prefixgetPrefix(Locales.ENGLISH, { mode: "no-prefix" });// Returns: { prefix: '', localePrefix: undefined }getPrefix(Locales.ENGLISH, { mode: "search-params" });// Returns: { prefix: '', localePrefix: undefined }

import { getPrefix, Locales } from "intlayer";// prefix-all: Always returns prefixgetPrefix(Locales.ENGLISH, {  mode: "prefix-all",  defaultLocale: Locales.ENGLISH,});// Returns: { prefix: '/en', localePrefix: 'en' }// prefix-no-default: No prefix when locale matches defaultgetPrefix(Locales.ENGLISH, {  mode: "prefix-no-default",  defaultLocale: Locales.ENGLISH,});// Returns: { prefix: '', localePrefix: undefined }// prefix-no-default: Returns prefix when locale differs from defaultgetPrefix(Locales.FRENCH, {  mode: "prefix-no-default",  defaultLocale: Locales.ENGLISH,});// Returns: { prefix: 'fr/', localePrefix: 'fr' }// no-prefix & search-params: Never returns prefixgetPrefix(Locales.ENGLISH, { mode: "no-prefix" });// Returns: { prefix: '', localePrefix: undefined }getPrefix(Locales.ENGLISH, { mode: "search-params" });// Returns: { prefix: '', localePrefix: undefined }

Practical Example

import { getPrefix, Locales } from "intlayer";// Build URLs with the appropriate prefix for a specific localeconst locale = Locales.FRENCH;const { prefix, localePrefix } = getPrefix(locale, {  defaultLocale: Locales.ENGLISH,  mode: "prefix-no-default",});// Using prefix for path constructionconst url1 = `/${prefix}about`.replace(/\/+/g, "/");// Result: "/fr/about"// Using localePrefix for locale identificationconsole.log(`Current locale: ${localePrefix}`);// Output: "Current locale: fr"

import { getPrefix, Locales } from "intlayer";// Build URLs with the appropriate prefix for a specific localeconst locale = Locales.FRENCH;const { prefix, localePrefix } = getPrefix(locale, {  defaultLocale: Locales.ENGLISH,  mode: "prefix-no-default",});// Using prefix for path constructionconst url1 = `/${prefix}about`.replace(/\/+/g, "/");// Result: "/fr/about"// Using localePrefix for locale identificationconsole.log(`Current locale: ${localePrefix}`);// Output: "Current locale: fr"

getLocalizedUrl: Generates a localized URL for a specific locale
getMultilingualUrls: Generates URLs for all configured locales

TypeScript

type GetPrefixResult = {  prefix: string; // The path prefix with trailing slash (e.g., 'fr/' or '')  localePrefix?: Locale; // The locale identifier without slashes (e.g., 'fr' or undefined)};function getPrefix(  locale: Locales,  options?: {    defaultLocale?: Locales;    mode?: "prefix-no-default" | "prefix-all" | "no-prefix" | "search-params";  }): GetPrefixResult;

type GetPrefixResult = {  prefix: string; // The path prefix with trailing slash (e.g., 'fr/' or '')  localePrefix?: Locale; // The locale identifier without slashes (e.g., 'fr' or undefined)};function getPrefix(  locale: Locales,  options?: {    defaultLocale?: Locales;    mode?: "prefix-no-default" | "prefix-all" | "no-prefix" | "search-params";  }): GetPrefixResult;

Why Intlayer ?