js-trie-router/README.md

@e22m4u/js-trie-router

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HTTP router for Node.js based on a prefix tree (trie).

• Supports path-to-regexp syntax.
• Parses JSON request body automatically.
• Parses query string and cookie header.
• Supports preHandler and postHandler hooks.
• Supports asynchronous handlers.

Installation

npm install @e22m4u/js-trie-router

To load the ES-module, you need to set "type": "module" in the package.json file, or use the .mjs extension.

Overview

A basic example of creating a router instance, defining a route and startup Node.js HTTP server.

import http from 'http';
import {TrieRouter} from '@e22m4u/js-trie-router';

const server = new http.Server(); // Node.js HTTP server
const router = new TrieRouter();  // TrieRouter instance

router.defineRoute({              // route definition
  method: 'GET',                  // request method "GET", "POST", etc.
  path: '/',                      // path template, example "/user/:id"
  handler(ctx) {                  // route handler
    return 'Hello world!';
  },
});

server.on('request', router.requestListener); // inject request listener
server.listen(3000, 'localhost');             // listen for requests

// Open in browser http://localhost:3000

Request context

The first parameter of a route handler is an instance of the RequestContext class which has a properties set with contents of a parsed incoming request.

• container: ServiceContainer instance of service container
• req: IncomingMessage native incoming request stream
• res: ServerResponse native server response stream
• params: ParsedParams key-value object with path parameters
• query: ParsedQuery key-value object with query string parameters
• headers: ParsedHeaders key-value object with request headers
• cookie: ParsedCookie key-value object of parsed cookie header
• method: string request method in uppercase, e.g. GET, POST, etc.
• path: string path including query string, e.g. /myPath?foo=bar
• pathname: string request path, e.g. /myMath

Example of accessing the context from a route handler.

router.defineRoute({
  method: 'GET',
  path: '/users/:id',
  handler(ctx) {
    // GET /users/10?include=city
    // Cookie: foo=bar; baz=qux;
    console.log(ctx.req);      // IncomingMessage
    console.log(ctx.res);      // ServerResponse
    console.log(ctx.params);   // {id: 10}
    console.log(ctx.query);    // {include: 'city'}
    console.log(ctx.headers);  // {cookie: 'foo=bar; baz=qux;'}
    console.log(ctx.cookie);   // {foo: 'bar', baz: 'qux'}
    console.log(ctx.method);   // "GET"
    console.log(ctx.path);     // "/users/10?include=city"
    console.log(ctx.pathname); // "/users/10"
    // ...
  },
});

Response sending

Return value of a route handler is used as response data. Value type affects representation of a response data. For example, if a response data is of type object, it will be automatically serialized to JSON.

value	content-type
string	text/plain
number	application/json
boolean	application/json
object	application/json
Buffer	application/octet-stream
Stream	application/octet-stream

Example of sending data as JSON.

router.defineRoute({     // register a route
  // ...
  handler(ctx) {         // incoming request handler
    return {foo: 'bar'}; // response will be encoded to JSON
  },
});

The request context ctx contains a native instance of the ServerResponse class from the http module, which can be used for manual response management.

router.defineRoute({
  // ...
  handler(ctx) {
    res.statusCode = 404;
    res.setHeader('content-type', 'text/plain; charset=utf-8');
    res.end('404 Not Found', 'utf-8');
  },
});

Route hooks

Defining a route with the defineRoute method allows to set up hooks to monitor and intercept requests and responses for a specific route.

• preHandler executes before calling a route handler
• postHandler executes after calling a route handler

preHandler

Before calling a route handler, operations such as authorization and request validation may be performed in the preHandler hook.

router.defineRoute({ // register a route
  // ...
  preHandler(ctx) {
    // called before the route handler
    console.log(`Incoming request ${ctx.method} ${ctx.path}`);
    // Incoming request GET /myPath
  },
  handler(ctx) {
    return 'Hello world!';
  },
});

A route handler will not be called if preHandler hook returns a value other than undefined and null, because that value will be sent as response data.

router.defineRoute({ // register a route
  // ...
  preHandler(ctx) {
    // return the response data
    return 'Are you authorized?';
  },
  handler(ctx) {
    // this handler will not be called
    // because the "preHandler" hook
    // has already sent the data
  },
});

postHandler

Return value of a route handler is passed to the second parameter of postHandler hook. It may be useful to modify the value before being sent.

router.defineRoute({
  // ...
  handler(ctx) {
    // return the response data
    return 'Hello world!';
  },
  postHandler(ctx, data) {
    // modify the response data before send
    return data.toUpperCase(); // HELLO WORLD!
  },
});

Global hooks

A TrieRouter instance allows to set up global hooks that have higher priority over route hooks and are called first.

• preHandler executes before calling a handler of each route
• postHandler executes after calling a handler of each route

Global hooks can be added using the addHook method of a router instance, where the first parameter is the hook name, and the second is a function.

router.addHook('preHandler', (ctx) => {
  // called before a route handler
});

router.addHook('postHandler', (ctx, data) => {
  // called after a route handler
});

Similar to route hooks, if a global hook returns a value other than undefined and null, that value will be sent as response data.

Debugging

Set the DEBUG variable to enable log output.

DEBUG=jsTrieRouter* npm run test

Testing

npm run test

License

MIT