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    Add Basic Logging to an Express 5 App with morgan

    expressExpress

    This lesson demonstrates using the morgan library to add basic logging to an express 5 application. We also log when the app starts up by passing a second argument to the app.listen() method.

    morgan

    The morgan logger has a whole list of pre-defined logging formats that you can use listed on their website. You can also build your own custom format. The format we chose for this lesson dev is a short-hand for the following :method :url :status :response-time ms - :res[content-length].

    Middleware

    Middleware are tiny programs that inspect and manipulate incoming requests in an express application. They can run before, after, or even in-between your other routes. They are commonly used for logging, authentication, and form processing.

    A thorough list of common middleware can be found on the express website here: http://expressjs.com/en/resources/middleware.html

    Middleware are typically added to your application with app.use(), but can also be added added to individual routes using app.get("/", middleware, routeHandler). While not recommended, multiple middleware can be added that way: app.get("/", middleware1, middleware2, routeHandler)

    While not covered in this lesson creating a middleware is easy and they have a lot in common with route handlers. Here is a simple logging middleware:

    app.use(function(res, res, next) {
        console.log(req.path);
        next();
    });