Node.js LogoIn Part II of this series: Making a Simple HTTP Server with Node.js – Part II we learned how to use the “path” and “file system” modules. By leveraging these Node.js modules, we were able to read the path of the HTTP request that our server received, and read from the file system of the web server. We also learned about the “__dirname” keyword, which provides an abstract reference to the folder in which the currently executing JavaScript file exists.

That version of our HTTP server simply checked to see if the request was for the file “index.html”, and if so, served it up. That was progress over Part I, but still not robust enough.

In this article, we will expand our Node.js HTTP server so that the following services are provided:

  • If an asset is requested, and it exists, it will be returned
  • If an asset is not specified, then “index.html” will be returned
  • If an asset is requested, and it does not exist, our custom 404.html page will be returned

We will make every effort to keep our three-step paradigm, which will, we hope, continue to illustrate that creating an HTTP web server with Node.js is at its core, quite simple. What we have to take a closer look at, is the fact that, as we ask more of our little web server, we have to roll up our sleeves and write the code that provides that very functionality.

So the good news is: It’s just more JavaScript. Yay!

Example # 1

In Example #1, we have the three-step core of our HTTP web server. We have already discussed each step in detail, so let’s just quickly re-cap:

Step # 1: Use the require() method to gain access to the Node.js modules that we need
Step # 2: Use the createServer() method of the HTTP module, and pass it a reference to our “requestHandler” function
Step # 3: Listen for a request on port # 3000

Simple, simple, simple.

Next, let’s look at two functions: our updated requestHandler() function, and then our new getFile() function.

Example # 2

In Example # 2, we first look at the request, and if no file was requested (i.e. the user simply typed into their browser), then we prepare to serve up “index.html”.

As we learned in Part II, the __dirname keyword provides an abstract reference to the folder in which the currently executing JavaScript file resides. We then create a variable named “page404”, which will provide a reference to our custom “404 / Not Found” page, should we need it.

Now we have everything we need, so we call the getFile() function, passing it the path and name of the asset we want (i.d. index.html), the response object, and then the reference to our custom 404 page.

Example # 3

In Example # 3, there are some new things happening. First, we use the exists() method of the file system object that was returned by the “fs” module, and assigned to our variable: “fs”. This method takes two arguments: a path to the file, and an anonymous function. That anonymous function takes one argument: “exists” (call it whatever you like). That single argument provides a helpful “truthy/falsy” flag against which we can test.

Folder Structure
The folder structure of this article’s example code

So if you take a moment to think about this, you’ll find that it’s quite cool: baked into the Node.js “fs” module is a method that simply tells us whether or not a named file exists. This is a perfect example of the brilliance of Node.js modules. Imagine how much heavy lifting you’d have to do if you needed to provide this kind of implementation yourself. Fortunately, someone did it for you. And that module can be used over and over again… a zillion more times if you like.

So moving along, if the “exists” argument returns a “truthy” value, we use the fs.readFile() method to literally read the physical file from the local file system. We have a little error checking to make sure that the file read operation did not fail, and if it did not fail, we send the contents of that file back to the user.

If the requested file was not found (i.e. the “exists()” method told us that the named file does not exist), then we serve up the custom 404.html file that we still have a reference to.

Example # 4

Example # 4 simply puts all our code examples together, to provide some context.


In this article we expanded our simple Node.js HTTP web server. We leveraged the exists() method of the “fs” (file system) object, to determine if the requested file actually exists, and provided logic that handles cases in which the requested file does not exist.

Helpful Links for the Node.js path and fs Modules


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