The simplest sitemap.xml generation plugin for Vite/Vue with ability to have alternate links for languages

generateSitemap.ts

import fs from 'fs/promises';
import path from 'path';
import {type Plugin} from 'vite';

const supportedLanguages: { [code: string]: string } = {
    'de': 'Deutsch',
    'en': 'English',
    'es': 'Español'
}

export interface SitemapOptionsRoutes {
    [path: string]: Array<{ [key: string]: string }>;
}

function generateSitemap(obj: { baseUrl: string, routes: string[] }): Plugin {
    const routes: SitemapOptionsRoutes = obj.routes.reduce<SitemapOptionsRoutes>((acc, route) => {
        acc[route] = Object.keys(supportedLanguages).map(lang => {
            const href = new URL(`${lang}${route}`, obj.baseUrl).toString();
            return {hreflang: lang, href};
        }).concat({hreflang: 'x-default', href: new URL(route, obj.baseUrl).toString()});
        return acc;
    }, {});

    return {
        name: 'yet-another-vite-plugin-sitemap',
        apply: 'build',
        async closeBundle() {
            let sitemap = '<?xml version="1.0" encoding="UTF-8"?>\n<urlset xmlns="http://www.sitemaps.org/schemas/sitemap/0.9" xmlns:xhtml="http://www.w3.org/1999/xhtml">\n';

            for (const route in routes) {
                if (routes.hasOwnProperty(route)) {
                    sitemap += `  <url>\n    <loc>${new URL(route, obj.baseUrl).toString()}</loc>\n`;

                    routes[route].forEach(alt => {
                        const attributes = Object.keys(alt).map(key => `${key}="${alt[key]}"`).join(' ');
                        sitemap += `    <xhtml:link rel="alternate" ${attributes}/>\n`;
                    });

                    sitemap += '  </url>\n';
                }
            }

            sitemap += '</urlset>';

            const outputPath = path.resolve('dist', 'sitemap.xml');

            await fs.mkdir(path.dirname(outputPath), {recursive: true});
            await fs.writeFile(outputPath, sitemap);
        },
    };
}

export default generateSitemap;

vite.config.ts

export default defineConfig({
    plugins: [
       vue(),

       generateSitemap({
            baseUrl: `https://somesite.com`,
            routes: [
                "/",
                "/page1",
                "/page1",
            ],
        }),
    ],
})