Express middleware: app.use and app.all

Question

Is there a difference between

app.use('/some/path', function(req, res, next() {})

and

app.all('/some/path', function(req, res, next() {})

They are both middleware functions that get called for /some/path requests only, right?

Answer 1

There is big difference between the use of these two examples. Functions registered with app.use are general middleware functions and is called appropriate to their position on the middleware stack, typically inside an app.configure function. This type of middleware is usually placed before app.route, with the exception of error handling functions.

On the other hand app.all is a routing function (not usually called middleware) which covers all HTTP methods and is called only inside app.route. If any of your previous router function matches the /some/path and did not call the next callback, app.all will not be executed, so app.all functions are usually on the beginning of your routing block.

There is also third type of middleware, used in your routing functions, eg.

app.get('/some/path', middleware1, middleware2, function(req, res, next) {}); 

which is typicaly used for limiting access or perform general tasks related to /some/path route.

For practical application you can use both functions, but be careful of the difference in behaviour when using app.use with /some/path. Unlike app.get, app.use strips /some/path from the route before invoking the anonymous function.

You can find more in the documentation of express.