Micro router for Cloudflare Workers

index.js

const router = require('./router');

router.setRoutes([
	{
		path: '/ping',
		method: 'GET',
		handler: ping
	},
	{
		path: '/hello/:name',
		method: 'GET',
		handler: sayHello
	},
]);

addEventListener('fetch', event => {
	event.respondWith(router.onRequest(event))
});

function ping() {
	return new Response('PONG!', {
		status: 200,
	});
}

function sayHello (request, params) {
	return new Response('Hello ' + params.name, {
		status: 200,
	});
}

router.js

const router = {
	routes: []
};

router.onRequest = async (event) => {
	try {
		const match = matchRoute(event.request, router.routes);

		if (match) {
			return await match.route.handler(event.request, match.params);
		} else {
			return new Response('No soup for you!', {
				status: 404,
			});
		}
	} catch (error) {
		return new Response(error.toString(), {
			status: 500,
		});
	}

}

// adds the routes config to the router
router.setRoutes = (routes) => {
	router.routes = routes.map((route) => {

		// we create the path components of the routes in advance so these are cached and doesn't have to be computed on each request
		route.pathComponents = route.path.split('/').map((component) => {

			const isParam = component.startsWith(':');
			const isOptional = component.startsWith('?');
			const paramName = isParam || isOptional ? component.substr(1) : null;

			return {
				string: component,
				isParam,
				isOptional,
				paramName
			}
		});
		return route;
	});
}


// matches a request with a route and returns a match object
function matchRoute (request, routes) {
	const url = new URL(request.url);
	const requestPath = url.pathname;

	for (const route of routes) {
		if (route.method.toLowerCase() === request.method.toLowerCase()) {
			const params = matchPath(route, requestPath);
			if (params) {
				return {
					route,
					params
				};
			}
		}
	}
}


// matches paths and returns an object with the values of the parameters
function matchPath (route, requestPath) {
	// If it's identical we simply return an empty object because there can be no params
	if (route.path === requestPath) return {};

	// We compare components of the two paths.
	// We've already created the components of the router path when the worker was initialized
	const requestPathComponents = requestPath.split('/');
	const params = {};

	for (var i = 0; i < route.pathComponents.length; i++) {
		const component = route.pathComponents[i];
		if (component.string !== requestPathComponents[i]) {
			// TODO: implement optional parameters
			if (component.isParam) {
				params[component.paramName] = requestPathComponents[i];
			} else {
				// if one component doesn't match and it's not a param then we return undefined and stop matching this path
				return;
			}
		}
	}

	return params;
}

module.exports = router;