How does ExpressJS determine if a requested resource is a "static" file? - express

Question

I'm using JSPM to manage my client side dependencies and serving files using ExpressJS
My Directory structure is
node_modules
routes
views
app.js
public
css
images
js
main.js
jspm_packages
system.js
npm
angular2#2.0.0-beta.7.js
I have static route setup in my Express app.js as follows:
app.use(express.static(path.join(__dirname, 'public')));
As expected when I request for GET /jspm_packages/system.js
it serves the file correctly
however when I request GET /jspm_packages/npm/angular2#2.0.0-beta.7.js
It gives me a 404 - not found.
I suspect some of those special characters in the file name are messing up express from resolving the request as a "static" file and using the correct static route.
How can I test if express is marking the request as "static"?
How can I overwrite the express regex (or whatever mechanism) express is using to mark a request as "static"?
How can I write a custom middleware using my own regex and forward the request to static instead?
thanks.

Answer 1

When working with express, you must make sure right middleware is registered in right order.
As per your question, How does express identifies a resource as static?, Actually express does not determine if its static or not, it does not even understand request types, what express does is execute proper middleware for given request.
When express receives a request, It goes and starts executing matching middleware in sequence until it runs out of them.
So in practice, you'll always register your static middleware first (just after request parsers and all), before your dynamic routes. Like shown below ...
var express = require('express');
var path = require('path');
var cookieParser = require('cookie-parser');
var bodyParser = require('body-parser');
var routes = require('./routes/index');
var app = express();
// view engine setup
app.set('views', path.join(__dirname, 'views'));
app.set('view engine', 'jade');
app.use(bodyParser.json());
app.use(bodyParser.urlencoded({ extended: false }));
app.use(cookieParser());
//Register your static middleware
app.use(express.static(path.join(__dirname, 'public')));
//Other cool code
app.use('/', routes);
Now, request will first go through express.static middleware, if it does not find a matching file, it will call next internally and pass request to next middleware in chain.
Meaning, suppose you have a static file in public directory named users and you have a route named routes.get('/users' ..... Now when user requests /users, the request will first pass to express.static and if it finds users file (which it does in this case), our route that we registered using routes.get will never get called. Now if you do the same but just remove the file named users from the public folder, then express.static middleware won't be able to find a matching file and will pass request to next middleware in chain i.e. routes.get(/users' ...`
Express does not assume or identify a resource as static by matching or using regular-expressions. If express.static middleware finds it, it will serve it else it will pass on the request to the next middleware in queue.
Though I was pretty sure, I tried to reproduce your issue, and I was served with the file with all the special characters in it, just as shown in following image.
Please reconfirm following:
Your express.static middleware gets registered first.
The resource you are trying to access exists, i.e. physical path exsists. (resource url are case insensitive, i.e. /USERS and /users both will match a file /public/users if it exists.
Make sure you don't have a typo.
If this does not resolve your issue, please share your app.js file, some content if you can't share all of it.
Hope this helps! Let me know if you need further assistance ... :)