I have just started studying node.js and express, the documentation of express on the home page is just too simple for me as a beginner.
for example,
app.configure('development', function(){
app.use(express.static(__dirname + '/public'));
...
});
It may seems very obvious to you, but I just wonder what express.static mean? I can't find an answer by searching Google.
This is just one example that I can't understand the code.
So is there any better documentation of express for the absolute beginner?
I agree that the Express documentation reads a bit more like a book than an API doc. In the case of express.static, this is a re-expored middleware from Connect (connect.static), which Express is built on. From the middleware section of the docs:
Typically with connect middleware you would require(‘connect’) like so:
var connect = require('connect');
app.use(connect.logger());
app.use(connect.bodyParser());
This is somewhat annoying, so express re-exports these middleware properties, however they are identical:
app.use(express.logger());
app.use(express.bodyParser());
You can see what middleware Connect exposes on their web site. In particular, check out the documentation for the static middleware.
express is the class and static is a member of that class. What express.static means is "use the static method of the express class", what the static method does is initialize a static file server to be served by your node.js server.
Related
Hi I need some help with how express handles routes.
In setting up my express app, I have something like this:
app.use(express.static('public'));
Next, I mount some api routes:
app.use('/api', myrouter);
app.get('*', function(req, res) {
res.sendFile(path.resolve('public/index.html'));
});
But, when the frontend requests data via an api route, e.g. at 'localhost:3000/api/things', I am seeing in the Express debug logs that at some point (unsure when) it actually tries to serve this request as a static file, like:
send stat "C:\myproject\public\api\things" +230ms
Even though this folder doesn't exist in 'public' and should be solely handled by my api. FYI, the handler for /api/things route is only implemented for the GET method, and does get invoked at some point.
How do I stop express server from also trying to serve api requests from the static folder?
Thanks very much.
Answering my own question... which appears to be a duplicate of this one:
`express.static()` keeps routing my files from the route
So the answer is this one: https://stackoverflow.com/a/28143812/8670745
In short, the app.use() declarations that mount your api routers should appear before the app.use() statements which tell express.static where to serve your static files from. This way, the latter acts as a catchall AFTER api route handling is done. Router engine order matters...
Your answer is misinformed, or rather you've misinterpreted the problem. Your original configuration:
app.use(express.static(__dirname + 'public'));
app.use('/api', myrouter);
Looks absolutely fine because there's no clash between the routes. The threads you've linked too aren't really the same, and I can see why moving the routes in those cases would have worked.
The only thing I'd say is your path to your static folder isn't reliable, you should really use path.join, or actually in your case you can just do express.static('public') - express will infer the folder your app is served from.
Actually, before I get into the question, when I do anything like
const app = express()
app is an instance of the entire express module right? Meaning, when I do app.route, route is it an Express method right or a NodeJS method, since Node has .route as well? Anyways... I just wanted to double check this.
app.route('/games')
.post(postGame)
.get(getGames);
app.route('/games/:id');
.get(getGame)
.delete(deleteGame);
Is this the same as... and if not... why would one choose one over the other?
app.get('/games');
app.post('/games');
app.get('/games/:id');
app.delete('games/:id');
Sorry, it's just been a while since I have used Express, and couldn't find anything about this specific problem. Thanks!
app is an instance of the entire express module right?
Yes, the app object is create by calling the top-level express() function exported by the Express module. That set the default http headers, render options.... and wrap the http node module:
app.listen = function listen() {
var server = http.createServer(this);
return server.listen.apply(server, arguments);
};
You can see more in the source code here (really readble)
route is it an Express method right or a NodeJS method
Route is an express object and nodeJs don't provide a routing system like express.
And for your example yes it's totally the same. They stores the handlers function in the same this._router.route
When I create a sample Express application using the express binary, the bootstrap code has these lines:
...
var app = express();
...
app.use(app.router);
I didn't find much about app.router. I thought that this is the middleware that handles the routing (app.get(), app.post() etc.) rules, but these rules also get executed when I remove the app.use(app.router); line.
So what is the exact purpuse of this middleware?
In Express 3.x, app.router is an enhanced version of the connect middleware router. As hector said, this is where Express handles the request handlers registered with app.get, app.post, etc.
If you do not call app.use(app.router) explicitly then express will call it implicitly the first time you use app.get(...), app.post(...), etc. However, you may want to .use it explicitly, because then you choose the order of all your middleware.
app.use(express.favicon());
app.use(express.bodyParser());
app.use(express.methodOverride());
// app.get, app.post, etc called before static folder
app.use(app.router);
app.use(express.static(path.join(__dirname, 'public')));
See how the router is retrieved in the Express 3 source here.
Note that Express 4 doesn't need app.router.
This is from the Express 2.x guide http://expressjs.com/2x/guide.html
"Note the use of app.router, which can (optionally) be used to mount
the application routes, otherwise the first call to app.get(),
app.post(), etc will mount the routes."
I suspect this applies to Express 3.x too.
In my case i wasn't exporting the module
module.exports = router;
This method has been deprecated
why we use router ..because of we need to connect our sub app to our main app.
Before I ask about app.router I think I should explain at least what I think happens when working with middleware. To use middleware, the function to use is app.use(). When the middleware is being executed, it will either call the next middleware by using next() or make it so no more middleware get called. That means that the order in which I place my middleware calls is important, because some middleware depends on other middleware, and some middleware near the end might not even be called.
Today I was working on my application and had my server running in the background. I wanted to make some changes and refresh my page and see the changes immediately. Specifically, I was making changes to my layout. I couldn't get it to work so I searched Stack Overflow for the answer and found this question. It says to make sure that express.static() is beneath require('stylus'). But when I was looking at that OP's code, I saw that he had his app.router call at the very end of his middleware calls, and I tried to figure out why that was.
When I made my Express.js application (version 3.0.0rc4), I used the command express app --sessions --css stylus and in my app.js file the code came setup with my app.router above both the express.static() and require('stylus') calls. So it seems like, if it comes already setup that way, then it should stay that way.
After re-arranging my code so I could see my Stylus changes, it looks like this:
app.configure(function(){
//app.set() calls
//app.use() calls
//...
app.use(app.router);
app.use(require('stylus').middleware(__dirname + '/public'));
app.use(express.static(__dirname + '/public', {maxAge: 31557600000}));
});
app.get('/', routes.index);
app.get('/test', function(req, res){
res.send('Test');
});
So I decided that the first step would be to find out why it is important to even have app.router in my code. So I commented it out, started my app and navigated to /. It displayed my index page just fine. Hmm, maybe it worked because I was exporting the routing from my routes file (routes.index). So next I navigated to /test and it displayed Test on the screen. Haha, OK, I have no idea what app.router does. Whether it is included in my code or not, my routing is fine. So I am definitely missing something.
So Here Is My Question:
Could somebody please explain what app.router does, the importance of it, and where I should place it in my middleware calls? It would also be nice if I got a brief explanation about express.static(). As far as I can tell, express.static() is a cache of my information, and if the application can't find the requested page, it will check the cache to see if it exists.
Note: This describes how Express worked in versions 2 and 3. See the end of this post for information about Express 4.
static simply serves files (static resources) from disk. You give it a path (sometimes called the mount point), and it serves the files in that folder.
For example, express.static('/var/www') would serve the files in that folder. So a request to your Node server for http://server/file.html would serve /var/www/file.html.
router is code that runs your routes. When you do app.get('/user', function(req, res) { ... });, it is the router that actually invokes the callback function to process the request.
The order that you pass things to app.use determines the order in which each middleware is given the opportunity to process a request. For example, if you have a file called test.html in your static folder and a route:
app.get('/test.html', function(req, res) {
res.send('Hello from route handler');
});
Which one gets sent to a client requesting http://server/test.html? Whichever middleware is given to use first.
If you do this:
app.use(express.static(__dirname + '/public'));
app.use(app.router);
Then the file on disk is served.
If you do it the other way,
app.use(app.router);
app.use(express.static(__dirname + '/public'));
Then the route handler gets the request, and "Hello from route handler" gets sent to the browser.
Usually, you want to put the router above the static middleware so that a accidentally-named file can't override one of your routes.
Note that if you don't explicitly use the router, it is implicitly added by Express at the point you define a route (which is why your routes still worked even though you commented out app.use(app.router)).
A commenter has brought up another point about the order of static and router that I hadn't addressed: the impact on your app's overall performance.
Another reason to use router above static is to optimize performance. If you put static first, then you'll hit the hard drive on every single request to see whether or not a file exists. In a quick test, I found that this overhead amounted to ~1ms on an unloaded server. (That number is much likely to be higher under load, where requests will compete for disk access.)
With router first, a request matching a route never has to hit the disk, saving precious milliseconds.
Of course, there are ways to mitigate static's overhead.
The best option is to put all of your static resources under a specific folder. (IE /static) You can then mount static to that path so that it only runs when the path starts with /static:
app.use('/static', express.static(__dirname + '/static'));
In this situation, you'd put this above router. This avoids processing other middleware/the router if a file is present, but to be honest, I doubt you'll gain that much.
You could also use staticCache, which caches static resources in-memory so that you don't have to hit the disk for commonly requested files. (Warning: staticCache will apparently be removed in the future.)
However, I don't think staticCache caches negative answers (when a file does not exist), so it doesn't help if you've put staticCache above router without mounting it to a path.
As with all questions about performance, measure and benchmark your real-world app (under load) to see where the bottlenecks really are.
Express 4
Express 4.0 removes app.router. All middleware (app.use) and routes (app.get et al) are now processed in precisely the order in which they are added.
In other words:
All routing methods will be added in the order in which they appear. You should not do app.use(app.router). This eliminates the most common issue with Express.
In other words, mixing app.use() and app[VERB]() will work exactly in the order in which they are called.
app.get('/', home);
app.use('/public', require('st')(process.cwd()));
app.get('/users', users.list);
app.post('/users', users.create);
Read more about changes in Express 4.
Routing means determining how an application responds to a client request to a particular endpoint, which is a URI (or path) and a specific HTTP request method (GET, POST, and so on).
Each route can have one or more handler functions, which are executed when the route is matched.
In Express 4.0 Router, we are given more flexibility than ever before in defining our routes.
express.Router() is use multiple times to define groups of routes.
route used as middleware to process requests.
route used as middleware to validate parameters using ".param()".
app.route() used as a shortcut to the Router to define multiple requests on a route
when we are using app.route(), we are attaching our app with that router.
var express = require('express'); //used as middleware
var app = express(); //instance of express.
app.use(app.router);
app.use(express.static(__dirname + '/public')); //All Static like [css,js,images] files are coming from public folder
app.set('views',__dirname + '/views'); //To set Views
app.set('view engine', 'ejs'); //sets View-Engine as ejs
app.engine('html', require('ejs').renderFile); //actually rendering HTML files through EJS.
app.get('/', function (req, res) {
res.render('index');
})
app.get('/test', function (req, res) {
res.send('test')
})
In express Version 4 we can easily define routes in the following manner:
server.js:
const express = require('express');
const app = express();
const route = require('./route');
app.use('/route', route);
// here we pass in the imported route object
app.listen(3000, () => console.log('Example app listening on port 3000!'));
route.js:
const express = require('express');
const router = express.Router();
router.get('/specialRoute', function (req, res, next) {
// route is now http://localhost:3000/route/specialRoute
});
router.get('/', function (req, res, next) {
// route is now http://localhost:3000/route
});
module.exports = router;
In server.js we imported the router object of the route.js file and apply it in the following manner in server.js:
app.use('/route', route);
Now all of the routes in the route.js have the following base URL:
http://localhost:3000/route
Why this approach:
The main advantage of taking this approach is that now our app is more modular. All the route handlers for a certain route now can be put into different files which makes everything more maintainable and easier to find.
An article by #kelyvinn from 2016, with the intent to demonstrate modularity, includes this code:
// controllers/apis/dogs/index.js
const
express = require('express'),
dogService = require('../../../services/dogs');
let router = express.Router();
router.get('/', dogService.getDogs);
router.get('/:id', dogService.getDogWithId);
module.exports = router;
I would like to know if it is possible to specify a subdirectory for the filesystem root or the document root for requests of static resources (if there's any such distinction) in node.js.
I know that I can do it by concatenating an absolute path from the root, but I'm wondering if it can be done on an application-wide level.
I haven't found anything in the documentation supports it, but perhaps I'm overlooking it.
EDIT: I should mention that I'm not interested in using a 3rd party library at this point.
Check out expressjs
http://expressjs.com/guide.html#configuration
Specifically
app.use(express.static(__dirname + '/public', { maxAge: oneYear }));
Express/connect has a 'static' middleware for this use case. There are other smaller packages just for static file serving, however, express is nice and well maintained.
The API does not allow you to do what you're asking for directly. You will need to use string concat.
I've tried the following script with nodejs and works well. it takes the current path as document root to serve.
app.js
var http = require('http');
var express = require('express');
var app = express();
app.use(express.static('./'));
var server = http.createServer(app);
server.listen(8080,'127.0.0.1',function() {
console.log('listen to 127.0.0.1:8080');
});
the reference is here:
http://expressjs.com/starter/static-files.html