Express is a server-side web framework that provides various features to assist in creating web applications.

Handlebars is templating language that provides additional functionality beyond static HTML files, including placeholder expressions and control flow helpers.

bin/

Contains the startup script; typically not necessary to modify

public/

Static assets like stylesheets, images, and client-side JavaScript files

routes/

Router files that contain router definitions that detail the actions that happen when defined paths are accessed

views/

Handlebars files that the routers will use to render HTML

app.js

Application setup, used by the startup script

package.json

Lists dependencies required by the application, as well as additional configuration

A route definition is made up of an HTTP method, a path, and a handler function. When a path is accessed using the specified HTTP method, the handler function will execute.

router.get('/', (req, res) => {
    // additional code here
    res.render('index', { title: 'Home Page' });
});

router.post('/submit', (req, res) => {
    // additional code here
    res.render('submit');
});

Router Handler Functions

The req argument is the request object and contains information about the HTTP request.

The res argument is the response object and is used in setting up and handling the response.

req.query

Contains query string variables; given path /collection?sortBy=name&order=asc req.query.sortBy will have the value of name req.query.order will have the value of asc

req.body

Contains post body variables

<form method="post">
    <input type="text" name="firstName">
    <button type="submit">Submit</button>
</form>

req.body.firstName will have the value of what was inputted into the text box

req.params

Contains values of route parameters. The route path definition can contain placeholders by prepending with a :

router.get('/users/:user', ...);

Give the path /users/kidddw , then req.params.user would contain kidddw .

res.render

res.render(viewString, localVariablesObject)

Responds with the rendered named view with the properties of localVariablesObject passed into the view

res.send

res.send(textString)

Responds with the raw text

res.json

res.json(variable)

Sends the JSON representation of the JavaScript variable