Node Beginner

Beginning tutorial for JavaScript and NodeJS

This contains the scripts created in the book.

The Application Stack

We're looking to create a complete web application. The parts we'll need are:

HTTP Server: serve web pages
Router: map requests to request handlers
Request handlers: fulfill requests
Request data handling: treat incoming POST data and pass to request handlers in a convenient form
View logic: create display content and send to user's browser
Upload handling: take care of the details of handling (image) uploads

Building the Application Stack

Separate the logic of the application using separate files and load into the main through modules.

Event-driven Asynchronous Callbacks

Node.js execution model only uses one single process. Therefore, any slow function calls results in massive slowdown within the entire process. Therefore, JavaScript and Node.js uses the concept of event-driven, asynchronous callbacks using an event loop.

As long as a function belongs to the asynchronous library, it calls the function with the passed in callback function. Once the code has been executed, Node.js enters the event loop, where it cycles waiting for events.

Understanding Node.js

Source: http://debuggable.com/posts/understanding-node-js:4bd98440-45e4-4a9a-8ef7-0f7ecbdd56cb

Eveything (in Node.js) runs in parallel, except your code. This is, all system code is executed in parallel, but all of your callback functions are executed in queue, although the order within the queue is not defined. In other words, no two function can access the same data structure at the same time.

For example, "in a web application, your main response time cost is usually the sum of time it takes to execute all your database queries. With node, you can execute all your queries at once, reducing the response time to the duration it takes to execute the slowest query." In this example, the execution of the query is done in parallel, while the callback functions passed into the query calls are passed back sequentially (I think that's what it means?).

Node is really good with low response times and high concurrency.

Creating a Module