http-router

HTTP request router for standard Request and Response.

---

Features

• Based on URL pattern API
• Web standard API compliant
• Declarative
• Functional programing pattern matching style
• Automatically HEAD request handler
• Nested route pathname
• Tiny
• Universal

Packages

The package supports multiple platforms.

• deno.land/x - https://deno.land/x/http_router/mod.ts
• npm - @httpland/http-router

URL router

URLRouter provides routing between URLs and handlers.

It accepts the URLPattern API as is. This means that various url patterns can be matched.

import { URLRouter } from "https://deno.land/x/http_router@$VERSION/mod.ts";
import { serve } from "https://deno.land/std@$VERSION/http/mod.ts";

const handler = URLRouter([
  [{ pathname: "/" }, () => new Response("Home")],
  [
    { password: "admin", pathname: "/admin" },
    (request, context) => new Response("Hello admin!"),
  ],
]);

await serve(handler);

It accepts a set of URLPatternInit and handlers wrapped by Iterable object.

In other words, it is not limited to arrays.

import { URLRouter } from "https://deno.land/x/http_router@$VERSION/mod.ts";

const handler = URLRouter(
  new Map([
    [{ pathname: "/" }, () => new Response("Home")],
  ]),
);

Pathname routes

URLPattern routes are the most expressive, but somewhat verbose. URL pattern matching is usually done using pathname.

URLRouter supports URL pattern matching with pathname as a first class.

import { URLRouter } from "https://deno.land/x/http_router@$VERSION/mod.ts";

const handler = URLRouter({
  "/api/students/:name": (request, context) => {
    const greeting = `Hello! ${context.params.name!}`;
    return new Response(greeting);
  },
  "/api/status": () => new Response("OK"),
});

same as:

import { URLRouter } from "https://deno.land/x/http_router@$VERSION/mod.ts";

const handler = URLRouter(
  [
    [
      { pathname: "/api/students/:name" },
      (request, context) => {
        const greeting = `Hello! ${context.params.name!}`;
        return new Response(greeting);
      },
    ],
    [{ pathname: "/api/status" }, () => new Response("OK")],
  ],
);

URL Route handler context

The URL route handler receives the following context.

Name	Description
pattern	URLPattern URL pattern.
result	URLPatternResult Pattern matching result.
params	URLPatternResult["pathname"]["groups"] URL matched parameters. Alias for result.pathname.groups.

URL match pattern

URL patterns can be defined using the URL pattern API.

• Literal strings which will be matched exactly.
• Wildcards (/posts/*) that match any character.
• Named groups (/books/:id) which extract a part of the matched URL.
• Non-capturing groups (/books{/old}?) which make parts of a pattern optional or be matched multiple times.
• RegExp groups (/books/(\\d+)) which make arbitrarily complex regex matches with a few limitations.

Check routes validity

The router never throws an error. If the route is invalid, it will be eliminated just.

To make sure that URLRoutes are valid in advance, you can use the validate function.

For example, ? as pathname is an invalid pattern.

import {
  URLRouter,
  URLRoutes,
  validateURLRoutes,
} from "https://deno.land/x/http_router@$VERSION/mod.ts";

const routes: URLRoutes = {
  "?": () => new Response(),
};
const result = validateURLRoutes(routes);

if (result !== true) {
  // do something
}

const handler = URLRouter(routes);

The validate function returns true in case of success, or an object representing the contents of the Error in case of failure.

Invalid route means the following:

• Invalid URLPattern
• Duplicate URLPattern

You are completely free to do this or not.

Nested route pathname

nest is nested URL pathname convertor. It provides a hierarchy of routing tables.

Hierarchical definitions are converted to flat definitions.

You can define a tree structure with a depth of 1. To nest more, combine it.

Example of a routing table matching the following URL:

• /
• /api/v1/users
• /api/v1/products
• /api/v2/users
• /api/v2/products

import {
  nest,
  URLRouter,
} from "https://deno.land/x/http_router@$VERSION/mod.ts";

const routeHandler = () => new Response();
const v2 = nest("v2", {
  users: routeHandler,
  products: routeHandler,
});
const api = nest("/api", {
  ...nest("v1", {
    users: routeHandler,
    products: routeHandler,
  }),
  ...v2,
});
const handler = URLRouter({ ...api, "/": routeHandler });

Concatenate path segment

Path segments are concatenated with slashes.

import { nest } from "https://deno.land/x/http_router@$VERSION/mod.ts";
import { assertEquals } from "https://deno.land/std@$VERSION/testing/asserts.ts";

const routeHandler = () => new Response();
assertEquals(
  nest("/api", {
    "/hello": routeHandler,
    "status/": routeHandler,
  }),
  {
    "/api/hello": routeHandler,
    "/api/status/": routeHandler,
  },
);

Ambiguous pattern

The routing table defined in nest may have duplicate url patterns in some cases.

As seen in Concatenate path segment, segment slashes are safely handled. This results in the following definitions being identical

• branch
• /branch

These are converted to the following pathname:

[root]/branch

In this case, the routing table is ambiguous.

Route with the same pattern always take precedence first declared route.

This is because pattern matching is done from top to bottom.

Pattern matching performance

Pattern matching is done from top to bottom. The computational complexity is usually O(n).

Pattern matching is done on URLs, so they are safely cached.

Already matched URL patterns have O(1) complexity.

HTTP request method router

MethodRouter provides routing between HTTP request methods and handlers.

import { MethodRouter } from "https://deno.land/x/http_router@$VERSION/mod.ts";
import { serve } from "https://deno.land/std@$VERSION/http/mod.ts";

const handler = MethodRouter({
  GET: () => new Response("From GET"),
  POST: async (request) => {
    const data = await request.json();
    return new Response("Received data!");
  },
});

await serve(handler);

HEAD request handler

By default, if a GET request handler is defined, a HEAD request handler is automatically added.

This feature is based on RFC 9110, 9.1

All general-purpose servers MUST support the methods GET and HEAD.

import { MethodRouter } from "https://deno.land/x/http_router@$VERSION/mod.ts";
import { serve } from "https://deno.land/std@$VERSION/http/mod.ts";
import { assertEquals } from "https://deno.land/std@$VERSION/testing/asserts.ts";

const handler = MethodRouter({
  GET: () => {
    const body = `Hello! world`;
    return new Response(body, {
      headers: {
        "content-length": new Blob([body]).size.toString(),
      },
    });
  },
});
const request = new Request("http://localhost", { method: "HEAD" });
const response = await handler(request);

assertEquals(response.body, null);
assertEquals(response.headers.get("content-length"), "12");

This can be disabled by setting withHead to false.

import { MethodRouter } from "https://deno.land/x/http_router@$VERSION/mod.ts";

const handler = MethodRouter({}, { withHead: false });

Hook on matched handler

The router provides hooks for cross-cutting interests.

Before each

Provides a hook to be called before the handler is invoked.

You can skip the actual handler call on a particular request by passing a Response object.

The handler call is skipped and the afterEach hook described below is called.

Example of handling a preflight request that is of transversal interest:

import { URLRouter } from "https://deno.land/x/http_router@$VERSION/mod.ts";
import { assertEquals } from "https://deno.land/std@$VERSION/testing/asserts.ts";
import { preflightResponse } from "https://deno.land/x/cors_protocol@$VERSION/mod.ts";

const handler = URLRouter({
  "/": () => new Response(),
}, {
  beforeEach: (request) => {
    const preflightRes = preflightResponse(request, {});
    return preflightRes;
  },
});

After each

Provides a hook that is called after each matching handler is called.

With this hook, you can monitor the handler's call and modify the resulting response.

To modify the response, a response object must be returned to the hook.

import { URLRouter } from "https://deno.land/x/http_router@$VERSION/mod.ts";
import { assertEquals } from "https://deno.land/std@$VERSION/testing/asserts.ts";

const handler = URLRouter({
  "/": () => new Response(),
}, {
  afterEach: (response) => {
    response.headers.set("x-router", "http-router");
    return response;
  },
});

assertEquals(
  (await handler(new Request("http://localhost"))).headers.get("x-router"),
  "http-router",
);
assertEquals(
  (await handler(
    new Request("http://localhost/unknown"),
  )).headers.get("x-router"),
  null,
);

Detect error in router

If your defined handler throws an error internally, it will be supplemented and safely return a Response.

Here is the default response on error.

HTTP/1.1 500 Internal Server Error

onError is called when an error is thrown internally by the handler. You may customize the error response.

import { URLRouter } from "https://deno.land/x/http_router@$VERSION/mod.ts";

const handler = URLRouter({
  "/": () => {
    throw Error("oops");
  },
}, {
  onError: (error) => {
    console.error(error);
    return new Response("Something wrong :(", {
      status: 500,
    });
  },
});

Spec

In addition to user-defined responses, routers may return the following responses:

Status	Headers	Condition
404		URLRouter If not all url pattern match.
405	allow	MethodRouter If HTTP method handler is not defined.
500		URLRouter, MethodRouter If an internal error occurs.

API

All APIs can be found in the deno doc.

Benchmark

Benchmark script with comparison to several popular routers is available.

deno task bench

Benchmark results can be found here.

Related

More detailed references:

• Term definition
• Developer's Guide

Recipes

URLRouter + MethodRouter

URLRouter and MethodRouter are independent, but will often be used together.

import {
  MethodRouter as $,
  URLRouter,
  URLRoutes,
} from "https://deno.land/x/http_router@$VERSION/mod.ts";

const routeHandler = () => new Response();
const routes: URLRoutes = {
  "/": $({
    GET: routeHandler,
  }),
  "/api/status/?": routeHandler,
  "/api/users/:id/?": (request, { params }) => {
    // params.id!
    return $({
      POST: routeHandler,
    })(request);
  },
};
const handler = URLRouter(routes);

Others

• router + compress

License

Copyright © 2022-present httpland.

Released under the MIT license