@inlang/paraglide-js/dist/compiler/runtime/extract-locale-from-header.test.js

[](https://inlang.com)

import { test, expect } from "vitest";
import { createParaglide } from "../create-paraglide.js";
import { newProject } from "@inlang/sdk";
test("returns the preferred locale from Accept-Language header", async () => {
    const runtime = await createParaglide({
        blob: await newProject({
            settings: {
                baseLocale: "en",
                locales: ["en", "fr", "de"],
            },
        }),
    });
    // simple direct match
    const request = new Request("http://example.com", {
        headers: {
            "Accept-Language": "en-US;q=0.8,fr;q=0.9,de;q=0.6",
        },
    });
    const locale = runtime.extractLocaleFromHeader(request);
    expect(locale).toBe("fr");
    // language tag match
    const request2 = new Request("http://example.com", {
        headers: {
            "Accept-Language": "en-US;q=0.8,nl;q=0.9,de;q=0.7",
        },
    });
    const locale2 = runtime.extractLocaleFromHeader(request2);
    // Since "nl" isn't in our locales, and "de" has the highest q-value after "nl"
    expect(locale2).toBe("en");
    // no match
    const request3 = new Request("http://example.com", {
        headers: {
            "Accept-Language": "nl;q=0.9,es;q=0.6",
        },
    });
    const locale3 = runtime.extractLocaleFromHeader(request3);
    expect(locale3).toBeUndefined();
});
test("returns undefined if no Accept-Language header is present", async () => {
    const runtime = await createParaglide({
        blob: await newProject({
            settings: {
                baseLocale: "en",
                locales: ["en", "fr", "de"],
            },
        }),
    });
    const request = new Request("http://example.com");
    const locale = runtime.extractLocaleFromHeader(request);
    expect(locale).toBeUndefined();
});