# package.json file

package.json file is used for storing information about your application as well as its dependencies. Usually, when managing your Nodejs application with git, you should ignore the node_modules folder (which contains all the dependencies). Instead, you can specify the library that your app use and then let npm install it automatically for you with npm install. Here is the default package.json file generated by express

You don’t even need to specify the dependencies manually. When you install any new package with npm, just add --save flag so that npm will update the package.json file automatically for you. For example

# app.js file

This is the main file for starting your web app. Actually, there is not much thing to care about this file since express generated it automatically for you. For a full list of all Express’ APIs, please visit Express - api reference. In this post, I only discuss about some important ones.

# Routing

Routing setting up in Express is straight-forward. You can define it inside your app.js file using the express app object. For example

Usually, the handler function for each request has 2 input arguments (the third one is next, which will be discussed later in Middleware section). They are req and res containing the information for request and response respectively. In the above example, when you access /, the handlerFunc1 will response by rendering the index view (see the next section for View in Express).

# Views

Express support defining views using ejs or jade template engine. I will choose ejs as the demonstration since it has the same syntax with normal markup HTML. If you want to use jade, it’s pretty similar for echoing the information sent from server. The difference is just about the markup style. All views are stored in views folder inside your web’s root directory with the file extension .ejs. Back to my previous example

After requesting to /, the handlerFunc1 will be activated. Express will then find the file index.ejs inside the views folder to render with an json object { title: 'Express' }. Below is an sample index.ejs file for this playing those information

As you can see, to echo the property in the response json object, you can use <%= propName %>. You can also include server-side js code inside <% %>. For example

This style is pretty much the same with other server side languages like php, asp,..

If you use <%= %> for HTML output, the markup tag will be escaped. To output raw HTML, use <%- %>

# Public resources

The resources (images, css, client-side javascript) is located inside public folder. For example, to include the file public/css/style.css inside your page

# Conclusion

That’s everything you need to know about the basics of Express. For the next post, I will give more information about the more advanced stuff of Express.