JavaScript Objects Coding Style Reviewed

Posted on December 3, 2010 by Stoimen

JS Objects

Once I posted about JavaScript object coding style. Back than I made the analogy with PHP array coding style. In breve it’s useful to format the arrays in PHP simply like that:

$data = array(
	'key1' => 'value1',
	'key2' => 'value2',
	'key3' => 'value3',
	'key4' => 'value4',
	'key5' => 'value5',
);

Note that there is a trailing comma after the last key/value pair. This is not a syntax error and helps you add new elements to the array with no fear to forget the comma. This coding standard is quite well known in the PHP community, but in fact writing JavaScript objects can be “translated” to something very similar. The only problem is that the trailing comma in JavaScript will result to an error, especially in Internet Explorer, so it is important to remove it.

var obj = {
	key1 : 'value1',
	key2 : 'value2',
	key3 : 'value3',
	key4 : 'value4',
	key5 : 'value5'
};

The problem is that when you’ve to add one key/value pair, you’ve to add the comma after the last pair. This actually makes it useless.

Better Solution

There is another way, much better I think, that may help you more when adding new pairs to the object.

var obj = 
	{ key1 : 'value1'
	, key2 : 'value2'
	, key3 : 'value3'
	, key4 : 'value4'
	, key5 : 'value5'
	};

In this example you can simply copy/paste the last pair and change the key and value, or you can simply can continue writing the way the object is constructed.

Thus you don’t have the problem with the last comma and syntax errors.

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Diving into Node.js – A Long Polling Example

Posted on December 2, 2010 by Stoimen

Node.js vs. The World

What is typical for most of the web servers is that they listen for requests and respond as quickly as possible on every one of them. In fact the speed of the response is one of the main targets of optimization for developers. Fast servers are what everyone needs. From web developers to website visitors!

In the field of the that battle different web servers have different “weapons” to gain time. While this is useful in most of the cases, when it comes to a chat-like applications and Node.js approaches, the response is not always immediately returned. As I described in my posts until now about Node.js, a simple web server may wait for an event to be emitted, and than return the response. Continue reading →

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Diving into Node.js – Very First App

Posted on November 19, 2010 by Stoimen

What do I have till now?

After Node.js is istalled, described in my previous post, I can simply run this command:

stoimenpopov:~# node server.js

and this will start the server with the code within server.js. But what’s the code of server.js?

Following the instructions of Node’s homepage and most of the tutorials I’ve found, I can simply copy/paste the code from the first lines of Node’s page:

var http = require('http');
http.createServer(function (req, res) {
  res.writeHead(200, {'Content-Type': 'text/plain'});
  res.end('Hello World\n');
}).listen(8124, "127.0.0.1");
console.log('Server running at http://127.0.0.1:8124/');

There are several things I find interesting in this code, making it different from JavaScript as we know it. First of all what is

var http = require(‘http’)

and why I need it? What is the purpouse of 8124 and 127.0.0.1?

Node is built in modules and to use one of them you must first include it with require. Just like the example above with require(‘http’). In the same manner you can include every module of Node.

What are the Node’s modules are pretty well described in the API page. Well I’d like to say that the API page is quite insufficient. That is very bad, cause most of the code you’ll need developing a node.js applicatoin isn’t described/explained there. Continue reading →

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Diving into Node.js – Introduction & Installation

Posted on November 16, 2010 by Stoimen

Why I Need Something Like Node.js?

First of all the use of some software is needed not because of itself, but because of the need of some specific functionality. In my case this was the need of real time news feed. Of course there is a way to make this without Node.js, as I’ll describe later in this post, but there are several disadvantages. However to begin from somewhere, let me explain what is Node.js.

Introducing Node.js

Perhaps the best way do describe what is Node.js is from its about page.

Node’s goal is to provide an easy way to build scalable network programs. In the “hello world” web server example above, many client connections can be handled concurrently. Node tells the operating system (through epoll, kqueue, /dev/poll, or select) that it should be notified when a new connection is made, and then it goes to sleep. If someone new connects, then it executes the callback. Each connection is only a small heap allocation.

…

In general Node is a program using the Google Chrome’s V8 JavaScript engine, which in turn is a program that can parse and execute code written in JavaScript. V8 is a very very interesting project itself. First of all from Google have developed this engine especially for one of his products – their browser Chrome. It pretends to be and by no means is one of the masterpieces of Google. It is fast and reliable engine, written in C++ and JavaScript, as Wikipedia’s page says. Actually this code is open source and can be embedded in whatever application written in C++. Thus you can have in your application a JavaScript engine. Continue reading →

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How to Make MP4 Progressive with qt-faststart

Posted on November 12, 2010 by Stoimen

A big part of the developers worldwide, who have dealt with video converting, sooner or later have been used FFMPEG. In fact I’d say that two of the main software on the video converting scene are FFMPEG and Mencoder. I began to use Mencoder back in 2005 and I used it as a DVD ripping tool, but my experience with it ends there, while now I use FFMPEG.

However FFMPEG is a converting program and many things depend on what kind of video files come as an input and what do you want to achieve as an output. Here comes the codec question, where various libraries can help. In my case, as I wrote few posts ago, I use MP4 as output encoded with h.264, both encoded with ffmpeg/libx264. So far so good, but there is one main problem that anyone used this pair knows.

Flash Player and MP4

As far as I know Flash Player 9 and beyond plays video files encoded with MP4/h.264 except the typical FLV (flash video files). This can help video sites not only to share their video content via web – within browser based flash players, but also to show them via some mobile device interface where MP4/h.264 is perhaps the only one reasonable solution. In this case the file is accessible in both medias.

By default Flash Player can play such FFMPEG encoded .mp4 files, but fist the whole file must be downloaded by the browser and only than the playback can begin. That’s because the FFMPEG puts meta info at the end of the video file, while the flash player needs it at the beginning and only than to begin playing while the file is still downloading.

qt-faststart

As the name of this software says this program helps you move the important meta info from the end to the beginning of the file. This helps the video to playback as early as possible. In an ideal circumstances everything works just fine, but there is a serious problem in fact.

qt-faststart and Server Crash

qt-faststart is responsible to move the meta info where it must be – at the beginning of the video file, but cannot finish execution when the video file is broken or the meta info doesn’t exists. Actually this is not a problem of qt-faststart, but to the video file. However this was a critical problem in my case, because the video files remains stuck for hours of execution and 99% of CPU usage.

Thankfully there is a solution and it can be found in the qt-faststart wrapper – qtfaststart.py

qtfaststart.py

written on Python this script overcomes the disadvantages of qt-faststart. As described by his author Daniel G. Taylor:

  1. Works everywhere Python can be installed
  2. Handles both 32-bit (stco) and 64-bit (co64) atoms
  3. Handles any file where the mdat atom is before the moov atom
  4. Preserves the order of other atoms
  5. Can replace the original file (if given no output file)

With its help not only qt-faststart doesn’t crash, but also the video files remain progressive as desired. The installation process is as difficult as copy/paste on the server where Python must be installed.

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