Background
I am testing a simple Hello World app using NodeJs v7 and express in cloud9.
I am trying to make my example work but I am failing.
Problem
All my cloud9 configurations are fine so that is not the problem. The problem is my app. When i debug, the route "api/v1/HolaBananas" never gets called and I don't know why!
Even worst, when i make the request, the browser just hangs, like it is waiting for an answer from the server that will never come!
Code
The index.js has the initialization and launch code. It is important for me that I keep this separate from api.js for modular reasons.
index.js
"use strict";
const express = require("express");
const app = express();
app.use("/api/v1", require("./api.js"));
app.listen(process.env.PORT);
console.log(`Server listening on port ${process.env.PORT}!`);
The api.js simply contains the routes and what they are supposed to do.
api.js
"use strict";
const express = require("express");
module.exports = function() {
const api = express.Router();
api.get("/HolaBananas", function(req, res){
res.send("hello bananas!");
});
return api;
};
Question
I am sure I am not using api.get in the right way, but I truly want to separate my initialization and launch code from the api.
How can I fix my code so it works?
Note
I am following the course
https://www.edx.org/course/introduction-mongodb-using-mean-stack-mongodbx-m101x-0
You can fix it by two following ways
var api = require("./api.js")();
app.use("/api/v1", require("./api.js"));
as API.js return a function reference. so you need to call that function to access route.
Or You need to modify your api.js as follows if you don't want to change index.js
"use strict";
const express = require("express");
const api = express.Router();
api.get("/HolaBananas", function(req, res){
res.send("hello bananas!");
});
module.exports = api;
Solution
While Vikash Sharma's solution would work, I figured it out by following the recommendation of Jayant Patil and to read this other question:
https://codereview.stackexchange.com/questions/51614/exporting-routes-in-node-js-express-4
Turns out we had the same issue, but the given answer to that question also allows me to encapsulate the api file completely inside a function, preserving its scope.
Still, kudos++ for trying!
There is one subtle thing about it: You have to invoke the function that you export in your api.js and use the router object that is returned from that function, so here is what you should do:
You have to replace this line:
app.use("/api/v1", require("./api.js"));
with this:
app.use("/api/v1", require("./api.js")());
Related
I'm starting with NodeJS and Express 4, and I'm a bit confused. I been reading the Express website, but can't see when to use a route handler or when to use express.Router.
As I could see, if I want to show a page or something when the user hits /show for example I should use:
var express = require('express')
var app = express()
app.get("/show", someFunction)
At the beginning, I thought this was old (for Express 3). Is that right or this is the way for Express 4 too?
If this is the way to do it in Express 4, what is express.Router used for?
I read almost the same example as above but using express.Router:
var express = require('express');
var router = express.Router();
router.get("/show", someFunction)
So, what's the difference between both examples?
Which one should I use if I just want to do a simple testing website?
app.js
var express = require('express'),
dogs = require('./routes/dogs'),
cats = require('./routes/cats'),
birds = require('./routes/birds');
var app = express();
app.use('/dogs', dogs);
app.use('/cats', cats);
app.use('/birds', birds);
app.listen(3000);
dogs.js
var express = require('express');
var router = express.Router();
router.get('/', function(req, res) {
res.send('GET handler for /dogs route.');
});
router.post('/', function(req, res) {
res.send('POST handler for /dogs route.');
});
module.exports = router;
When var app = express() is called, an app object is returned. Think of this as the main app.
When var router = express.Router() is called, a slightly different mini app is returned. The idea behind the mini app is that each route in your app can become quite complicated, and you'd benefit from moving all that code into a separate file. Each file's router becomes a mini app, which has a very similar structure to the main app.
In the example above, the code for the /dogs route has been moved into its own file so it doesn't clutter up the main app. The code for /cats and /birds would be structured similarly in their own files. By separating this code into three mini apps, you can work on the logic for each one in isolation, and not worry about how it will affect the other two.
If you have code (middleware) that pertains to all three routes, you can put it in the main app, before the app.use(...) calls. If you have code (middleware) that pertains to just one of those routes, you can put it in the file for that route only.
Express 4.0 comes with the new Router. As mentioned on the site:
The express.Router class can be used to create modular mountable route
handlers. A Router instance is a complete middleware and routing
system; for this reason it is often referred to as a “mini-app”.
There is a good article at https://scotch.io/tutorials/learn-to-use-the-new-router-in-expressjs-4 which describes the differences and what can be done with routers.
To summarize
With routers you can modularize your code more easily. You can use routers as:
Basic Routes: Home, About
Route Middleware to log requests to the console
Route with Parameters
Route Middleware for Parameters to validate specific parameters
Validates a parameter passed to a certain route
Note:
The app.router object, which was removed in Express 4, has made a comeback in Express 5. In the new version, it is a just a reference to the base Express router, unlike in Express 3, where an app had to explicitly load it.
How they are different
Everyone, including the documentation, tends to refer back to how much they are the same, but not actually reference any differences. Well, they are, in fact, different.
var bigApp = express();
var miniApp = express.Router();
listen()
The most obviously difference is that the bigApp will give listen, which just a rather confusing way to do what would otherwise be simple and obvious the node http or https module:
var server = require('http').createServer(bigApp);
server.listen(8080, function () {
console.info(server.address());
});
I consider this an anti-pattern because it abstracts and obscures away something that wasn't complicated or difficult in the first place, and then makes it difficult for people to use websockets and other middleware that require the raw http server.
Internal State
The big difference, which is really important, is that all bigApps have separate internal state.
bigApp.enable('trust proxy');
bigApp.enabled('trust proxy');
// true
var bigApp2 = express();
bigApp2.enabled('trust proxy');
// false
bigApp.use('/bunnies', bigApp2);
// WRONG! '/bunnies' will NOT trust proxies
A miniApp passed to a bigApp, however, will be operated by the bigApp in such a way that its internal state and thisness will be preserved and those routes will behave accordingly.
bigApp.enable('trust proxy');
bigApp.enabled('trust proxy');
// true
var miniApp = express.Router();
bigApp.use('/bunnies', miniApp);
// CORRECT! All state and such are preserved
This can be a big deal because express does a lot of (sometimes trixy) things to the http.ServerRequest and httpServerResponse object - such as modifying (or hijacking) req.url and req.originalUrl and various other properties you've been using without realizing - and you probably don't want that duplicated and separated.
Smaller API
There is a smaller, more well-defined number of functions a Router can use:
.use(mount, fn)
.all(mount, fn)
.options(mount, fn)
.head(mount, fn)
.get(mount, fn)
.post(mount, fn)
.patch(mount, fn)
.put(mount, fn)
.delete(mount, fn)
.route(mount).XXXX
.param(name, cb).XXXX
There are a few other convenience methods as well, such as basic(), but you won't find set() or enable() or other methods that change the larger app state.
app.route('/book')
.get(function (req, res) {
res.send('Get a random book')
})
.post(function (req, res) {
res.send('Post a random book')
})
As in above example, we can add different HTTP request method under a route.
Let’s say your application is little complex. So what we do first is we divide the application into multiple modules so that changes in one module doesn't clutter the others and you can keep working on individual modules, but at the end of the day you need to integrate everything into one since you are building a single application. It is like we have one main application and few child applications whose parent is the main application.
So when we create the parent application we create one using
const express = require("express");
const parent = express();
And to this parent application we need to bring in the child applications. But since the child applications are not totally different applications (since they run in the same context - java term), express provides the way to do it by means on the Express's Router function and this is what we do in the each child module file and lets call one such child module as aboutme.
const express = require("express");
export const router = express.Router();
By export we are making this module available for other to consume and since we have modularized things we need to make the module files available to the parent application by means of node's require function just like any other third party modules and the parent file looks something like this:
const express = require("express");
const parent = express();
const child = require("./aboutme");
After we make this child module available to the parent, we need to tell the parent application when to use this child application. Lets say when a user hits the path aboutme we need the child application about me to handle the request and we do it by using the Express's use method:
parent.use("/aboutme", child);
and in one shot the parent file looks like this:
const express = require("express");
const parent = express();
const child = require("./aboutme");
parent.use("/aboutme", child);
Above all what the parent can do is it can start a server where as the child cannot. Hope this clarifies. For more information you can always look at the source code which takes some time but it gives you a lot of information.
using app.js to write routes means that they are accessible to all the users as app.js is loaded on application start. However, putting routes in express.router() mini apps protect and restrict their accessibility.
In a word , express.Routercan do more things when compares to app.get(),such as middleware, moreover, you can define one more router object with express.Router()
express.Router has many options:
enable case sensitivity: /show route to not be the same as /Show, this behavior is disabled by default
strict routing mode: /show/ route to not the same as /show, this behavior is also disabled by default
we can add specific middleware/s to specific routes
In one of the questions in the quiz this was asked: "express.Router() creates an object that behaves similar to the app object."
The correct answer is 'True'. I know that we can both create routers by using either of the two but is it safe to say that they are not the same in all cases? If my understanding is correct, the express() variable can do more things like start a server while the other one cannot.
In a complicated application, app is module, for example article and user. router is controller or action in module, for example article create and list.
E.g the url https://example.com/article/create parse article module and create router.
also app and router can be level-in-level.
Hie,
I am developing a Nodejs (Express) web app and pretty much new to this technology. So far I see that there can only be one point of entry mine being my the server.js file. Now it seems all requests and/or processes should be initiated here which is fine for a smaller application, but my site has about 25 page routes already all of who's request should be handle here. I also have a dozen or so Ajax requests are handled here. Now even though I am processing different functions e.g CRUD operations in separate files, I still fear at some point my code will become unreadable as the server.js file get longer
const express = require("express")
const path = require("path")
const exphbs = require("express-handlebars")
let app = express()
app.set("views",path.join(__dirname,'templates'))
app.engine('handlebars',exphbs({defaultLayout:'main'}))
app.set('view engine','handlebars')
app.set('port',(process.env.PORT || 3000));
app.get('/',(req,res)=>{
res.render('home',{'title':'Home'});
});
app.get('/home',(req,res)=>{
res.render('home',{'title':'Home'});
});
app.get('/register',(req,res)=>{
res.render('register',{'title':'Register'});
});
app.use(express.static(path.join(__dirname, '/public')));
app.listen(app.get('port'),()=>{
console.log(`Server started on port : ${app.get('port')}`)
})
So far my server.js is this small, but it just hit me that I have 25 pages and multiple Ajax processes on each.
Yes, you have to structure your routes. For that, you have to look at Express Router. You have to create different route files based on a specific resource.
/routes/homeRoutes.js
const express = require("express");
const router = express.Router();
router.get('/',(req,res)=>{
res.render('home',{'title':'Home'});
});
module.exports = router;
server.js
const homeRoutes = require("./routes/homeRoutes");
app.use("/api/v1/home", homeRoutes);
Also, have a look at the following links for a better understanding of project structure and express router.
https://expressjs.com/en/guide/routing.html
project structure
I think what you are looking for is splitting the code up in local modules. You can place parts of your code in separate files, include module.exports at the end and then require(./filename.js) them in your server.js.
You can see an example here: https://www.tutorialsteacher.com/nodejs/nodejs-local-modules
I am a long time programmer but I'm new to Node and have a simple question about routing paths in Express which I cannot get to the bottom of.
I've developed a very simple app using node/express and MySql. I have then split up my GET and POST routes in the app just for convenience. I am using the route '/posts' at the app level and the sub route '/submit-form' in my router() which is the URL my form submits to.
I'm obviously doing something stupid because it doesn't work, I get the cannot POST message. If I use the full URL in the app and in the router then it works fine so there's nothing wrong with the code I think, only with my understanding of how express does routing.
Any advice appreciated.
A router should be used with the .use() method. Therefore, you should use the following in your app.js file
app.use('/posts', PostRoute)
When the nested router (on /posts) will handle the request, it will now based on the nested route declaration which HTTP method should match
app.js
const app = express();
app.use('/user', require('./routes/user'))
then inside the user;
const router = express.Router({});
router.post('/login', (req,res,next) => {
});
module.exports = router;
I am following an on-line tutorial of implementing in MEAN. Everything looks great. Except when it comes to routes. I understand that routes need to be in a javascript files (js extension). It's okay with a small web site. But as the number of requests grow, I would like to put them in separate files. I looked up in SOF for how to include files in Javascript. It is non-trivial. Has anyone faced this issue before? Can anyone comment?
Thanks
You can use Router Middleware by using express.Router(). This allows you to break your routes into different files. On a side note, middleware is very powerful and is worth learning about, its a huge part of Express.
Say you have an app that has a /users section. You can create a separate routes file called users.js that contains all routes that pertain to your /users resources. Then inside your server.js where your main Express app is listening, you can assign the users.js routes to the /users resource using app.use().
You can have as many routers as you'd like, all routes are read top-down when Express is deciding which route to use.
./routes/users.js
// Create an express router
var router = require('express').Router();
// Define a route for GET /
router.get('/', function(req, res) {
res.status(200).send('Welcome to /users');
});
// make our router available for require() statements
module.exports = router;
server.js
var express = require('express');
var app = express();
// Users routes
var users = require('./routes/users');
// Tell our app to use the Users routes defined in ./routes/users.js
app.use('/users', users);
app.listen(process.env.PORT || 3000, function() {
console.log('listening');
});
I'm starting with NodeJS and Express 4, and I'm a bit confused. I been reading the Express website, but can't see when to use a route handler or when to use express.Router.
As I could see, if I want to show a page or something when the user hits /show for example I should use:
var express = require('express')
var app = express()
app.get("/show", someFunction)
At the beginning, I thought this was old (for Express 3). Is that right or this is the way for Express 4 too?
If this is the way to do it in Express 4, what is express.Router used for?
I read almost the same example as above but using express.Router:
var express = require('express');
var router = express.Router();
router.get("/show", someFunction)
So, what's the difference between both examples?
Which one should I use if I just want to do a simple testing website?
app.js
var express = require('express'),
dogs = require('./routes/dogs'),
cats = require('./routes/cats'),
birds = require('./routes/birds');
var app = express();
app.use('/dogs', dogs);
app.use('/cats', cats);
app.use('/birds', birds);
app.listen(3000);
dogs.js
var express = require('express');
var router = express.Router();
router.get('/', function(req, res) {
res.send('GET handler for /dogs route.');
});
router.post('/', function(req, res) {
res.send('POST handler for /dogs route.');
});
module.exports = router;
When var app = express() is called, an app object is returned. Think of this as the main app.
When var router = express.Router() is called, a slightly different mini app is returned. The idea behind the mini app is that each route in your app can become quite complicated, and you'd benefit from moving all that code into a separate file. Each file's router becomes a mini app, which has a very similar structure to the main app.
In the example above, the code for the /dogs route has been moved into its own file so it doesn't clutter up the main app. The code for /cats and /birds would be structured similarly in their own files. By separating this code into three mini apps, you can work on the logic for each one in isolation, and not worry about how it will affect the other two.
If you have code (middleware) that pertains to all three routes, you can put it in the main app, before the app.use(...) calls. If you have code (middleware) that pertains to just one of those routes, you can put it in the file for that route only.
Express 4.0 comes with the new Router. As mentioned on the site:
The express.Router class can be used to create modular mountable route
handlers. A Router instance is a complete middleware and routing
system; for this reason it is often referred to as a “mini-app”.
There is a good article at https://scotch.io/tutorials/learn-to-use-the-new-router-in-expressjs-4 which describes the differences and what can be done with routers.
To summarize
With routers you can modularize your code more easily. You can use routers as:
Basic Routes: Home, About
Route Middleware to log requests to the console
Route with Parameters
Route Middleware for Parameters to validate specific parameters
Validates a parameter passed to a certain route
Note:
The app.router object, which was removed in Express 4, has made a comeback in Express 5. In the new version, it is a just a reference to the base Express router, unlike in Express 3, where an app had to explicitly load it.
How they are different
Everyone, including the documentation, tends to refer back to how much they are the same, but not actually reference any differences. Well, they are, in fact, different.
var bigApp = express();
var miniApp = express.Router();
listen()
The most obviously difference is that the bigApp will give listen, which just a rather confusing way to do what would otherwise be simple and obvious the node http or https module:
var server = require('http').createServer(bigApp);
server.listen(8080, function () {
console.info(server.address());
});
I consider this an anti-pattern because it abstracts and obscures away something that wasn't complicated or difficult in the first place, and then makes it difficult for people to use websockets and other middleware that require the raw http server.
Internal State
The big difference, which is really important, is that all bigApps have separate internal state.
bigApp.enable('trust proxy');
bigApp.enabled('trust proxy');
// true
var bigApp2 = express();
bigApp2.enabled('trust proxy');
// false
bigApp.use('/bunnies', bigApp2);
// WRONG! '/bunnies' will NOT trust proxies
A miniApp passed to a bigApp, however, will be operated by the bigApp in such a way that its internal state and thisness will be preserved and those routes will behave accordingly.
bigApp.enable('trust proxy');
bigApp.enabled('trust proxy');
// true
var miniApp = express.Router();
bigApp.use('/bunnies', miniApp);
// CORRECT! All state and such are preserved
This can be a big deal because express does a lot of (sometimes trixy) things to the http.ServerRequest and httpServerResponse object - such as modifying (or hijacking) req.url and req.originalUrl and various other properties you've been using without realizing - and you probably don't want that duplicated and separated.
Smaller API
There is a smaller, more well-defined number of functions a Router can use:
.use(mount, fn)
.all(mount, fn)
.options(mount, fn)
.head(mount, fn)
.get(mount, fn)
.post(mount, fn)
.patch(mount, fn)
.put(mount, fn)
.delete(mount, fn)
.route(mount).XXXX
.param(name, cb).XXXX
There are a few other convenience methods as well, such as basic(), but you won't find set() or enable() or other methods that change the larger app state.
app.route('/book')
.get(function (req, res) {
res.send('Get a random book')
})
.post(function (req, res) {
res.send('Post a random book')
})
As in above example, we can add different HTTP request method under a route.
Let’s say your application is little complex. So what we do first is we divide the application into multiple modules so that changes in one module doesn't clutter the others and you can keep working on individual modules, but at the end of the day you need to integrate everything into one since you are building a single application. It is like we have one main application and few child applications whose parent is the main application.
So when we create the parent application we create one using
const express = require("express");
const parent = express();
And to this parent application we need to bring in the child applications. But since the child applications are not totally different applications (since they run in the same context - java term), express provides the way to do it by means on the Express's Router function and this is what we do in the each child module file and lets call one such child module as aboutme.
const express = require("express");
export const router = express.Router();
By export we are making this module available for other to consume and since we have modularized things we need to make the module files available to the parent application by means of node's require function just like any other third party modules and the parent file looks something like this:
const express = require("express");
const parent = express();
const child = require("./aboutme");
After we make this child module available to the parent, we need to tell the parent application when to use this child application. Lets say when a user hits the path aboutme we need the child application about me to handle the request and we do it by using the Express's use method:
parent.use("/aboutme", child);
and in one shot the parent file looks like this:
const express = require("express");
const parent = express();
const child = require("./aboutme");
parent.use("/aboutme", child);
Above all what the parent can do is it can start a server where as the child cannot. Hope this clarifies. For more information you can always look at the source code which takes some time but it gives you a lot of information.
using app.js to write routes means that they are accessible to all the users as app.js is loaded on application start. However, putting routes in express.router() mini apps protect and restrict their accessibility.
In a word , express.Routercan do more things when compares to app.get(),such as middleware, moreover, you can define one more router object with express.Router()
express.Router has many options:
enable case sensitivity: /show route to not be the same as /Show, this behavior is disabled by default
strict routing mode: /show/ route to not the same as /show, this behavior is also disabled by default
we can add specific middleware/s to specific routes
In one of the questions in the quiz this was asked: "express.Router() creates an object that behaves similar to the app object."
The correct answer is 'True'. I know that we can both create routers by using either of the two but is it safe to say that they are not the same in all cases? If my understanding is correct, the express() variable can do more things like start a server while the other one cannot.
In a complicated application, app is module, for example article and user. router is controller or action in module, for example article create and list.
E.g the url https://example.com/article/create parse article module and create router.
also app and router can be level-in-level.