@public-tech/express-helpers v0.1.7

express-helpers

Utilities to help with using express on node.

This library only has a single runtime dependency on debug for debugging statements (DEBUG=Routes).

Compatibility

• Requires node 8+

• Requires express 4+

Rationale

This module attempts to add the following abilities to your code:

• you don't need to require in any services into the server.js file. This means you only have to add service classes to your services directory and they will be picked up automatically and have their routes registered.

• you don't need to remember to add routes to express - you just add them to the routes object of the service you are working on.

• keeping your routes co-located with the service code that will be called from the route handler, keeps all your related code in one place

• using express middleware with async/await syntax can be seen as cleaner or more preferable

Usage

Routes is a class that will load all your routes and register the routes with express.

Given a class UserRoutes, you need to expose a routes property. You need to add the routes and give the handler function that will implement the route. You specify routes per http verb, e.g. get, post, put, delete..

//UserRoutes.js

const { helpers } = require('express-helpers');

UserRoutes = {};

//`routes` needs to be accessible on the module
UserRoutes.routes = {
    get: [
      { path: '/user/:email',
        funcs: [
          someMiddleWare,
          helpers.awaitHandlerFactory(async (req, res, next) => {
            const result = await someAsyncProcess();
          }),
          anotherFunction(req, res, next)
        ]
      }
    ],
    post: [
      { path: '/user',
        funcs: [
          helpers.awaitHandlerFactory(async (req, res, next) => {
            //lots of awesome code
          });
        ]
      }
    ]
};

module.exports = UserRoutes;

In the above code, you add adding an express route that handle a HTTP GET request to /user/:email and a route that will handle a post request to /user.

You specify and array of handler functions per route and specify routes per HTTP verb. Currently, GET, POST, PUT and DELETE are the supported verbs.

You will notice that each handler function is the result of calling helpers.awaitHandlerFactory. This helper function (found in the helpers module) wraps a handler function so that you can use async/await syntax in your handler function. This is optional.

Once you have added routes properties, you can then register all the routes with express. You should place all your routes in the same directory. Keeping your routes separate from your services will allow for easy unit and integration testing.

Given an app structure of:

in server.js, when you initialise express, you can then register all the routes for all the routes in the routes directory:

const express = require('express');
const { Routes } = require('express-helpers');

const app = express();
const pathPrefix = '/my-app';
const routes = new Routes(app, path.join(__dirname, './routes'), pathPrefix);

//add all handlers to the express app
routes.addAllRoutes();
//or add routes by verb, e.g. add all post routes using routes.addPostRoutes(), or add all delete routes..

This will register every Route module that exposes a routes property that is found in the routes directory. In addition, this will then register every get route for every registered module with the express app. You need to pass the absolute path to the routes directory to the Routes. The pathPrefix is optional and will append the prefix to every route, e.g. a prefix of my-app will mean that the path to handlers looks like: /my-app/user/:email.

Alternativly, you can directly register a routes object with the express app:

const express = require('express');
const { Routes } = require('express-helpers');

const app = express();
const routes = new Routes(app); //don't register any Routes objects from a directory
const someRouteObj = {
  get: [{ path: '/somepath', funcs: [someFunc] }]
};

routes.addRawRoutes(someRouteObj);

This is useful when unit/integration testing your app and you just want to test a route without creating a dummy Routes module.

• add400Handlers()

This will add 400 handlers for any route that is not already handled.

const express = require('express');
const { Routes } = require('express-helpers');

const app = express();
const pathPrefix = '/my-app';
const routes = new Routes(app, path.join(__dirname, './routes'), pathPrefix);

routes.addAllRoutes();
routes.add400Handlers(); //anything not handled by the registered handlers will end up here.

Typescript routes

Routes in typescript are also supported, with the following syntax in the routes file:

import { helpers } from 'express-helpers';

export const routes = {
  get: [
    {
      path: '/typescript-get',
      funcs: [
        /* eslint no-unused-vars: off */
        helpers.awaitHandlerFactory(async (req, res, next) => {
          // ... your code here
        })
      ]
    }
  ],
  post: [
    {
      path: '/typescript-post',
      funcs: [
        /* eslint no-unused-vars: off */
        helpers.awaitHandlerFactory(async (req, res, next) => {
          // ... your code here
        })
      ]
    }
  ]
};

helpers

This module exposes some small helper functions. To use the module:

const { helpers } = require('express-helpers');`

• writeResponse

This function wrapes sending an express response and sets the statusCode if the handler errorred.

• logErrors

This function is a small express middleware to log errors to stderr.

• sendErrorToClient

This function is a small express middleware to sanitise any error before sending to the client.

You can use these function like so:

app.use(helpers.logErrors);
app.use(helpers.sendErrorToClient);
// ... add other stuff to express
app.listen(port, hostname);

This will ensure that all errors are logged on the server but none are leaked to the client. With the logErrors and sendErrorToClient middlewares enabled, your route handling code just needs to call next on an error:

helpers.awaitHandlerFactory(async (req, res, next) => {
  try {
    const result = await someAsyncProcess();
    if (result.success) {
      //do awesome things
    }
  } catch (err) {
    next(err); //will log the error on the server (console) and then call `sendErrorToClient` with the error;
  }
});

• sendInvalidApiCall

This function is a small express middleware that will send a 400 error to the caller;

• awaitHandlerFactory

This function allows you to use async/await syntax within handler functions.

helpers.awaitHandlerFactory(async (req, res, next) => {
  const result = await someAsyncProcess();
  if (result.success) {
    //do awesome things
  }
});