Express Route Discovery

If you've ever poked around an Express app, you know that the "routes" don't exist, except as a discoverable graph of handlers. This package will build simple data structures of the routes of an app, for the purposes of inspection, documentation, or testing.

Discovering your routes

Importing this module gives you the discovery factory. Pass it some Express app, and it will return a RouteTree.

const app = require('express')();
const discover = require('express-route-discovery');
 
// ... mount all your routes/routers/etc.
 
app.locals.routes = discover(app);

If you print out your routes as JSON, it might look something like this:

[
  {
    "id": "postapiusers",
    "path": "/api/users",
    "method": "POST",
    "stack": [
      "query",
      "expressInit",
      "<anonymous>",
      "logger",
      "urlencodedParser",
      "jsonParser",
      "methodOverride",
      "serveStatic",
      "session",
      "errorHandler",
      "addUserToDatabase"
    ]
  },
  {
    "id": "getapiprofilesusername",
    "path": "/api/profiles/:username",
    "method": "GET",
    "stack": [
      "query",
      "expressInit",
      "<anonymous>",
      "logger",
      "urlencodedParser",
      "jsonParser",
      "methodOverride",
      "serveStatic",
      "session",
      "errorHandler",
      "fetchUserByUsername",
      "getUsersProfiles",
      "respond"
    ]
  }
]

But why?

There are two main uses for this package: information and testing.

For informational purposes, you may decide you want to mount the route tree on your app.locals (after, of course, all routes have been mounted). The RouteTree and its component Routes both implement a toJSON method. So, if you would like to print a list of your routes and their associated handler stacks, it can be done just with JSON.stringify(discover(app)). You will definitely want to name your handler functions.

Or you may want this for testing purposes. If you have a route tree, you can find a route and its associated layers. What that means is you can use something like sinon to stub/spy certain middleware layers as needed.

A short performance note: The factory function runs quickly enough, but it is also memoized. After calling it once on some app object, it will return the same tree on subsequent calls (this can be overridden if you need).

Data Structures

RouteTree

A route tree encapsulates all the Routes of a given app. It provides a basic interface for finding Routes.

Method: RouteTree.find

• Signature :: (RegExp | String) => (Route | Undefined)
• The argument to this function will be matched against the target Route's id (e.g., "getusersfriends"). If the argument is a string, it must be an exact match; if a regular expression, it will return the first route whose id matches.

Method: RouteTree.findAll

• Signature :: (RegExp | String) => Array<Route?>
• The argument may be a string, but this is more for finding many Routes by some regexp.

Route

A route is a representation of an HTTP endpoint. It can be uniquely identified by the HTTP method and path (and that is how we identify them here). Its "value" is an orderered stack of all the connect-based handlers that have been mounted on its parent routers.

Internally, the objects in this stack are references to Express.Layer objects. (This class is a private one; this package works for express v4 and above.) Since these references point to the actual router's layers, please use caution if you want to alter these objects.

Shape: Route

Method: Route.layer

• Signature :: (String) => (Layer | Undefined)
• Internally, this simply looks at the route's stack and finds the appropriate layer.

Layer

A layer is a direct reference to the Express.Layer object for some piece of middleware. Alter it only with caution.

Shape: Layer

There are other properties, which you can inspect in a repl, but these are the important ones: