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Title The Node Beginner Book: A Comprehensive starucarulrap.ml Tutorial; Author(s) Manuel Kiessling; Publisher: starucarulrap.ml (April 6, ); eBook (last. The Node Beginner Book. A starucarulrap.ml tutorial by Manuel Kiessling The complete text is available as a DRM-free eBook (PDF, ePub and Kindle format). The Node Beginner Book book. Read 47 reviews from the world's largest community for readers. The aim of The Node Beginner Book is to get you started with.
Furthermore, we don't want to write only the most basic code to achieve the goal, however elegant and correct this code might be. We will intentionally add more abstraction than necessary in order to get a feeling for building more complex Node. The application stack Let's dissect our application. Which parts need to be implemented in order to fulfill the use cases? We want to serve web pages, therefore we need an HTTP server Our server will need to answer differently to requests, depending on which URL the request was asking for, thus we need some kind of router in order to map requests to request handlers To fulfill the requests that arrived at the server and have been routed using the router, we need actual request handlers The router probably should also treat any incoming POST data and give it to the request handlers in a convenient form, thus we need request data handling We not only want to handle requests for URLs, we also want to display content when these URLs are requested, which means we need some kind of view logic the request handlers can use in order to send content to the user's browser Last but not least, the user will be able to upload images, so we are going to need some kind of upload handling which takes care of the details Let's think a moment about how we would build this stack with PHP.
Which in turn means that the whole "we need to be able to serve web pages and receive HTTP requests" stuff doesn't happen within PHP itself. Well, with node, things are a bit different. Because with Node. In fact, our web application and its web server are basically the same. This might sound like a lot of work, but we will see in a moment that with Node.
Let's just start at the beginning and implement the first part of our stack, the HTTP server. Do I need to have everything in one file? What if I want to make sure that my code stays readable the more stuff I implement? Turns out, it's relatively easy to keep the different concerns of your code separated, by putting them in modules. This allows you to have a clean main file, which you execute with Node.
So, let's create a main file which we use to start our application, and a module file where our HTTP server code lives. My impression is that it's more or less a standard to name your main file index.
It makes sense to put our server module into a file named server. Let's start with the server module. Create the file server. Passing functions is not only a technical consideration. With regard to software design. Just think. Routing to real request handlers Back to business. Building the application stack 29 about it: It only needs to get something done. Our HTTP server and our request router are now best friends and talk to each other as we intended.
Go read it now. Building the application stack 30 Right now. At this point we need to make a decision: This allows us to wire the request handlers into the router.
New application part. Although dependency. Building the application stack 31 injection. This means we need to pass the request handlers from our server into our router. A varying number of items. How are we going to pass them? Right now we have two handlers. I propose we name it like a verb. Building the application stack 32 Objects have different properties and methods.
Now if only the request handlers could actually send something back to the browser. Making the request handlers respond Beautiful. How to not do it The straight-forward approach we.
And opening http: Building the application stack 35 Server has started. We start with the request handlers and make them return what we would like to display in the browser. We need to change requestHandlers. Likewise, the router needs to return to the server what the request handlers return to him. We therefore need to edit router. As you can see, we also return some text if the request could not be routed. And last but not least, we need to refactor our server to make it respond to the browser with the content the request handlers returned via the router, transforming server.
If we start our rewritten application, everything works like a charm: Ok, then why is that a problem? The short answer: Blocking and non-blocking As said, the problems will arise when we include non-blocking operations in the request handlers.
As always. Building the application stack 40 Of course.
We did so because it allows us to make use of a very simple yet useful non-blocking operation: Building the application stack 41 to make proper use of non-blocking operations.
Please modify it to reflect the following file requestHandlers. We are going to use our start request handler for this again. Once again.
In our example. And while we are at it. If you would like to prove this. In this example. What the code does is straightforward: Building the application stack 42 What exec does is. The problem is that exec. Thinking about a more expensive command makes this more obvious: Building the application stack 43 function error.
But how can we achieve our goal. Which is why the callback is called relatively expeditious. To be more precise. Our new approach is as follows: Dangerous stuff. Enough explanation. But one possible solution for this is. Quite often. Right now. Instead of expecting a return value from the route function. Next comes router. If no request handler can be used. Building the application stack 46 function route handle. Same pattern: And last but not least.
The start handler will respond from within the anonymous exec callback. If we start our application again node index.
Our handler functions need to accept the response parameter. This will make HTTP requests to http: For the sake of simplicity we will assume that only image files are going to be uploaded and displayed through the application.
Our server. Building the application stack 49 Serving something useful Until now. We will first look at how to handle incoming POST requests but not file uploads.
This author likes to hear himself talking way too much anyways. Upon receiving and handling this request. We will present a textarea that can be filled by the user and submitted to the server in a POST request. You should see this very simple form when requesting http: Now that we are becoming expert novices.
If not. I decided to not include that extra level of abstraction i. Which makes sense. I hear you: This is done by adding listeners to the request object that is passed to our onRequest callback whenever an HTTP request is received. This basically looks like this: Building the application stack 52 multiple megabytes in size. To make the whole process non-blocking. We currently can access the request object in our server only. We need to tell Node. Handling the whole bulk of data in one go would result in a blocking operation.
These events are data an new chunk of POST data arrives and end all chunks have been received. I suggest we handle the POST data processing right in the server and pass the final data on to the router and the request handlers. The question arises where to implement this logic. In my opinion.
Building the application stack 53 Thus. Here we go. Put small amounts of text into the textarea as well as lots of text.
Adding the console logging on every chunk that is received probably is a bad idea for production code megabytes of POST data. We basically did three things here: I suggest playing around with this a bit.
We also pass the POST data into the router. Building the application stack 54 http.
Building the application stack 55 function route handle. And in requestHandlers. My plan is to constantly expand The Node Craftsman Book while collecting and using feedback from the community. Thus, I decided to release a first version of the new book as early as possible. This way, you have the following advantages: Learn: Get your hands on new chapters covering advanced Node. It goes way beyond your typical Hello World tutorial.