express-locale
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Express middleware to determine locale
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express-locale [](https://github.com/smhg/express-locale/actions/workflows/ci.yml)
==============
Express middleware to determine the [locale identifier](https://en.wikipedia.org/wiki/Locale_(computer_software)) of the incomming request.
It returns (only) full locale identifiers based on the middleware's configuration. Configuration defines possible sources, their order and, optionally, a whitelist. For performance reasons, on each request, remaining lookups are ignored as soon as a match is found.
> Use version 1.x for Express 3 support and/or older Node versions.
## Installation
`npm install --save express-locale`
## Usage
```javascript
import express from 'express';
import createLocaleMiddleware from 'express-locale';
express()
.use(createLocaleMiddleware())
.use((req, res) => {
res.end(`Request locale: ${req.locale}`);
})
.listen(3000);
```
The `locale` property on the request object will contain an object with these properties:
```json
{
"source": "default",
"language": "en",
"region": "GB"
}
```
When using this object in a string context, its `toString` method returns the locale identifier (`en-GB` in the example above).
**Note:** only full locales (language-REGION) are returned, but a [mapping](#map) of languages to a default locale can be provided as a lookup.
## Configuration
You can pass a configuration object to `createLocaleMiddleware()` with the default being:
```json
{
"priority": ["accept-language", "default"],
"default": "en-GB"
}
```
This tells the middleware to use 2 sources in order: `accept-language`, which has no configuration, and `default` which is set to `en-GB`.
The name of the lookup used in the priority list always matches the configuration key.
Type: `Array` Default value `['accept-language', 'default']`
Defines the order of lookups. The first lookup to return a full locale will be the final result.
Built-in lookups:
* `cookie`
* `query`
* `hostname`
* `accept-language`
* `map`
* `default`
Read below on how to add [custom lookups](
Type: `Object` Default value `'{name: 'locale'}'`
The `name` of the cookie that contains the locale for the cookie lookup.
Use with [cookie-parser](https://github.com/expressjs/cookie-parser) middleware.
**Note:** you are responsible for writing the locale to the cookie.
Type: `Object` Default value `'{name: 'locale'}'`
The `name` of the query string parameter that contains the locale for the query lookup.
Type: `Object` Default value `{}`
A mapping of hostnames to locales for the hostname lookup.
Type: `Object` Default value `{}`
Maps lookup results that return only a language to a full locale.
Type: `String` Default value `'en-GB'`
The default locale for the default lookup.
Type: `Array` Default value `undefined`
Lookup results are validated against this list of allowed locales if provided.
Type: `String` Default value `'locale'`
By default, the locale is attached to `req.locale` but can be configured with the `requestProperty` option.
Add custom lookups or overwrite the default ones by using the `lookups` property:
```javascript
createLocaleMiddleware({
priority: ['custom'],
lookups: {
custom: (req) => req.ip === '127.0.0.1' ? 'en-US' : undefined
}
});
```