Express 4 Routes Using Socket.io - javascript

Having a rough time adding Socket.io in my Express 4 Routes. In my routes/index.js I have:
var express = require('express');
var router = express.Router();
/* GET home page. */
router.get('/', function (req, res, next) {
res.render('index', { title: 'Express' });
});
router.post('/message', function(req, res) {
console.log("Post request hit.");
// res.contentType('text/xml');
console.log(appjs);
io.sockets.emit("display text", req);
// res.send('<Response><Sms>'+req.body+'</Sms></Response>');
});
module.exports = router;
but io is undefined. I have seen several examples of how to do this, but none that worked for me. Any help would be appreciated.

You need to pass your socket.io variable to the router module so that it has access. You could do this by wrapping your module in a function call.
var express = require('express');
var router = express.Router();
/* GET home page. */
var returnRouter = function(io) {
router.get('/', function(req, res, next) {
res.render('index', {
title: 'Express'
});
});
router.post('/message', function(req, res) {
console.log("Post request hit.");
// res.contentType('text/xml');
console.log(appjs);
io.sockets.emit("display text", req);
// res.send('<Response><Sms>'+req.body+'</Sms></Response>');
});
return router;
}
module.exports = returnRouter;
Then, whever you import this route you would call this function like: require(./routefile)(io)
Here's a good article about creating modules that require being passed a variable: Node.Js, Require and Exports

How about exploiting events? This could add an extra layer of self-awareness to the app, including socket messaging.
Since express's app() inherits from node's eventEmitter, I app.emit('EVENT_NAME', payload) at any point in my route handlers,
and then just handle that with app.on('EVENT_NAME', function(payload){})
with any logic available. I'm using it in my current setup.

This is super old, but I was looking to do the same thing and didn't find a suitable answer. I came up with a good solution using app.set('socketio', io) and req.app.get('socketio') in my route. I was then able to create a reference to the sender's socket in my route without using io.on().
See the answer I added here for the code:
Use socket.io inside a express routes file

Related

Hot reloading with express and chokidar causes a http headers sent error when using multiple routes

I've been trying a variety of setups for hot reloading and one that I've come across is the https://github.com/glenjamin/ultimate-hot-reloading-example/. Modifying this boilerplate code as a starting point, I've come across the following problem in my server code:
// server.js
import chokidar from 'chokidar';
import express from 'express';
const app = express();
// this is the middleware for handline all of my routes
app.use(function (req, res, next) {
require('./server/index')(req, res, next);
// if I commented out any additional routes, the setup would work fine
require('./server/foo')(req, res, next);
require('./server/catch-all')(req, res, next);
});
//this watches the server folder for changes
const watcher = chokidar.watch('./server');
watcher.on('ready', function () {
watcher.on('all', function () {
console.log("Clearing /server/ module cache from server");
Object.keys(require.cache).forEach(function (id) {
if (/[\/\\]server[\/\\]/.test(id)) delete require.cache[id];
});
});
});
app.listen(3000, 'localhost', function (err) {
if (err) throw err;
const addr = this.address();
console.log('Listening at http://%s:%d', addr.address, addr.port);
});
The above is the server code that handles clearing the cache by watching for changes with the chokidar module. If I have just one route required inside the app.use middleware function (which listens for every incoming request), I can get it to work. However if have multiple routes, the following error occurs:
Error [ERR_HTTP_HEADERS_SENT]: Cannot set headers after they are sent to the client
This is a common issue posted on stack overflow, but all of the solutions I've come across and attempted haven't worked. My route files are as follows:
//index.js
import express from 'express';
const router = express.Router();
router.get('/', (req, res, next) => {
res.send("greagrehgarhegrehuh").end();
return next('router');
});
module.exports = router;
//end of index.js
//foo.js
import express from 'express';
const router = express.Router();
router.get('/foo', (req, res, next) => {
res.send("foo").end();
return next('router');
});
module.exports = router;
//end of foo.js
//catch-all.js
import express from 'express';
const router = express.Router();
router.get('*', (req, res, next) => {
res.send("catch all").end();
return next('router');
});
module.exports = router;
// end of catch-all.js
All three routes do the same thing, bar the endpoint. So far I've explicitly called end on each to end the response, used return next('router') to skip the rest of the middleware functions and have also tried doing it without the above as well. Any ideas on what I'm missing here to get this working? Here's a github project that showcases the issue
https://github.com/RonanQuigley/express-chokidar-hot-reload
UPDATE
So I actually removed the next calls and seem to have almost got it working by doing the following:
app.use(function (req, res, next) {
require('./server/index')(req, res, next);
require('./server/foo')(req, res, next);
});
// a second app.use middleware, that does the same
// as the catch all // * router.get from my original post
app.use(function (req, res, next) {
app.get('*', (req, res) => res.send('catch all'));
})
However, I can't use this second app.use with another require call to a file with an express router like the others. So it seems that express runs through the middleware stack, reaches the * and tries to set the header twice.
The reason I need the * is normally if a user requests an endpoint that doesn't exist, Node correctly shows up with cannot GET/. However, for some reason, with the setup I've outlined express will then crash. My workaround is using * at the end of the middleware stack and I'd just use a res.redirect to send the user back to wherever, but this causes the above issue I've outlined in my original post. So not sure how to get around that one.
So currently I have either:
1) Hot reloading works without the require for a router.get('*'), but when the user navigates to an endpoint that doesn't exist, express will crash.
2) Hot reloading works with the app.get('*') inside a second app.use call, but I can't then use a router to move this into a separate file.
Okay, so posting this solution up for my own future reference and in case somebody else stumbles into this problem.
After speaking with the express devs, it turns out that this is indeed possible with a combination of the following:
// you need to use comma separated routes
app.use(
dynamic('./server/index'),
dynamic('./server/foo')
);
// require the library at runtime and apply the req, res, next arguments
function dynamic(lib) {
return function (req, res, next) {
return require(lib).apply(this, arguments)
}
}
In the case of webpack, this would break it as you can't use require as an expression. So use the following to get around that:
function createRoutes(router) {
const dynamic = (lib) => {
return function (req, res, next) {
// let webpack generate a regex expression from this require
// if we don't you would get a critical dependency warning
// which would result in the routes not being found
return require("./src/" + lib + ".js").apply(this, arguments);
}
}
router.use(
dynamic('index'),
dynamic('foo'),
);
return router;
}
Let's step back a bit and talk about middleware.
Say you have a function which runs some kind of middleware.
const runMiddleware = (req, res, next) => {
console.log(`this will run everytime a HTTP request comes in`);
}
Then to use that middleware within express:
app.use(runMiddleware);
Every time any (GET, POST, DELETE, etc) request comes in, this function is run.
Essentially you are doing the same thing below - You are wrapping three (3) route calls with a single function. This function is calling all of these routes at once, hence res is actually being sent 3 times in a row in the example below:
app.use(function (req, res, next) { // runs every time any request comes in
require('./server/index')(req, res, next); // res sent, ok
require('./server/foo')(req, res, next); // res sent, err
require('./server/catch-all')(req, res, next); // res sent, err
});
Here is a basic way of handling routes:
const index = require('./server/index');
const foo = require('./server/foo');
app.use('/', index);
app.use('/foo', foo);
// catch everything else
app.use(function (req, res) {
res.send('catch all');
})

Correct format for Node architecture (BASIC)

Introduction
I have built some back end functionality in Node (First time using Node). Problem is that the whole thing was built in one page (index.js) so now im following a few basic tutorials and setting out express router middleware and now trying to follow a modular MVC approach,
This code is simple but brakes when I separate into two pages Server.js and config.js. I know its a simple problem but i cant spot it. can someone help spot the problem and maybe improve the structure ?
Problem
I go to http://localhost:8080/about or a different route and I get
Cannot GET /about
rather than the correct print out.
back-end/server.js
var express = require('express');
var app = express();
var port = process.env.PORT || 8080;
// get an instance of router
var router = express.Router();
// START THE SERVER
// ==============================================
app.listen(port);
console.log('Server has started!! ' + port);
back-end/config.js
router.use(function(req, res, next) {
console.log(req.method, req.url);
next();
});
router.get('/', function(req, res) {
res.send('im the home page!');
});
// sample route with a route the way we're used to seeing it
router.get('/sample', function(req, res) {
res.send('this is a sample!');
});
router.get('/about', function(req, res) {
res.send('im the about page!');
});
app.route('/login')
.get(function(req, res) {
res.send('this is the login form');
})
.post(function(req, res) {
console.log('processing'); // shows on console when post is made
res.send('processing the login form!'); // output on postman
});
app.use('/', router);
As #SLaks said in his comment, you need to import (require) your backend/config.js file. But it's not as simple as that...
In node, variables are scoped to the file in which they appear, so if you simply add require('./config') to your server.js file, that's not going to work either, because the router variable in config.js is local to that file - it's not going to know about the router variable in server.js.
The solution to this is to have the config.js file export a function which the server.js file can use to configure stuff. For example
config.js
module.exports = function(router) {
// set up your router here with router.use, etc.
};
server.js
var configure = require('./config');
// after you set up your express router...
configure(router);
// now start listening

Module.Exports not working for Express

I'm trying to organize routes in express. But I'm having trouble getting a simple setup to work. I have two files, api.js, which has the routing info, and index.js, which runs the server.
However, when I try this, I get no response on localhost:3000.
api.js
var express = require('express');
module.exports = function() {
var router = express.Router();
router.get('/', function(req, res) {
res.send('im the home page!');
});
return router;
}
index.js
var express = require('express');
var app = express();
var router = require('./api');
app.use('/',router);
app.listen(3000);
console.log('Listening on port 3000!');
However, when I change api.js to this, it works:
api.js
var express = require('express');
var router = express.Router();
router.get('/', function(req, res) {
res.send('im the home page!');
});
module.exports = router;
I don't understand why the bottom api.js works when the top one doesn't. Shouldn't module.exports return the same express Router in both cases?
The difference is that in the first version you're exporting a function that returns the router vs the second version where you're exporting the router itself.
In the first version, Express calls your exported function, passing it req and res, expecting it to somehow handle the request. The exported function of course is not designed to handle a request (it's just creating a router and returning it), so the request times out.

Multiple level of routing using Express.js with Node.js

I'm new to javascript. I'm trying to make a RESTfull API using Node.js and Express.js
My directory structure is as follows
/server.js
/api/api.js
/api/location/location.js
I want to make the API modular. I want that all the requests (get/post/delete/push) beginning with /api/* to be handled by api.js and whatever routing be required, api.js should route it to proper module.
For example, if someone requests GET /api/location/abc/xyz then api.js will transfer control to location.js which will then transfer to abc.js which will finally transfer to xyz.js stored in directory /api/location/abc/xyz/xyz.js
How can I achieve this?
Code so far:
/server.js
var express = require('express');
var app = express();
var api = require('./api/api.js');
var location = require('./api/location/location.js');
//app.use('/api/location', location); //This works, but I want api.js to handle sub-routes!
app.use('/api', api);
app.get('/', function(req, res){
res.end('successful get/');
});
app.listen(12345);
/api/api.js
module.exports = function(req, res, next) {
res.end('successful get /api');
next();
};
//Add code to handle GET /api/location
/api/location/location.js
module.exports = function(req, res, next){
res.end('from location!');
next();
}
You would use express.Router([options]).
And write it that way:
/api/api.js
var router = require('express').Router();
router.get('/location', require('./api/location') );
module.exports = router;
/api/api/location.js
module.exports = function(req, res, next){
res.end('from location!');
}
And don't call next(); if you ended the response. You only call next() in your callback if you don't handle the response.
I don't know how complex your REST api will be later. But try to to keep the routing in a small number of file. Having a callback for the routing in an own file like /api/api/location.js is most likely not the best idea.

I am having trouble understanding Node.js code

I am having trouble understanding this Node.js code:
I understand importation of the module 'express' and using the Router constructor.
var express = require('express');
var router = express.Router();
/* GET home page. */
router.get('/', function(req, res) {
res.render('index', { title: 'Express' });
});
module.exports = router;
However, I don't understand the purpose of '/', 'index' in the following part:
router.get('/', function(req, res) {
res.render('index', { title: 'Express' });
});
Some help would be greatly appreciated.
The function of 'index' is that it defines which view to render
res.render(view, [locals], callback)
The function of '/' can be explained by
// invoked for any requested passed to this router
router.use(function(req, res, next) {
// .. some logic here .. like any other middleware
next();
});
// will handle any request that ends in /events
// depends on where the router is "use()'d"
router.get('/events', function(req, res, next) {
// ..
});
You can use this page for future reference :
http://expressjs.com/api.html#res.render
If your site is abc.com, then in simple terms, / means the when somebody is coming to your site and he places abc.com in browser then execute the following function.
url is relative, so / means root.
.render('index'... means that render the index.html or index.ejs that you would be having in your project. Rendering means that send it in the response to the browser.
Node is great, but this is one of their few absolutely horrid APIs.
app.get() with a single String argument gets a property previously set via set(). Basic getter / setter stuff.
app.get() with a String and a function means when they do an HTTP GET to this path, call this function.
Bad bad overloading.

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