Monday vhandit #1

This is the first post in a series of articles called "Monday vhandit". You can go to the original post by clicking on each head title.

Character encodings: essential concepts

This article points out why Unicode matters and differentiates among concepts: character sets, coded character set (unit is code points), and character encoding.

Explained from First Principles: the Internet

The very structural and well-explained article contains almost concepts of the Internet. I really appreciated the author's effort put on that post.

Dev Community - DevDojo

I just joined this community. DevDojo is really a developer-oriented platform. It is very nice, easy, fast, and sufficient to write (Markdown supported) and search for a post. The best of it, you also have a personal blog for your posts at "<your_username>.devdojo.com". My username is vnnvanhuong

Everything you need to know about HTTP security headers

A good collection of HTTP security-related headers. Moreover, its content is structured in a timeline manner when a header is introduced to solve a specific problem.

A history of elliptic curves in tweets

A very fun and creative post for knowing more about the history of elliptic curves. It is fun for me because I am reading "Random Curves: Journeys of a Mathematician" by Neal Koblitz.

Comments

What the heck is Meteor DDP?

I was using Meteor for my messenger project. I was so curious about the real time connection. I wanted to know how exactly this mechanism works. In this post, I will go through the DDP Specification, an overview of WebSocket, and a simple demo about how to subscribe a publication of Rocket.Chat (containing a DDP server) from an external webpage. At a glance, I knew that Meteor invented a protocol called DDP which uses for handling real time connection. So then, what is DDP? "DDP (Distributed Data Protocol) is the stateful WebSocket protocol that Meteor uses to communicate between the client and the server." [1] All right! Why does DDP matter? "DDP is a standard way to solve the biggest problem facing client-side JavaScript developers: querying a server-side database, sending the results down to the client, and then pushing changes to the client whenever anything changes in the database" . [2] In order to understand deeply the protocol, I decided ...

Strategy Design Pattern

For example, I have a program with an Animal abstract class and two sub-classes Dog and Bird. I want to add new behavior for the class Animal, this is "fly". Now, I face two approaches to solve this issue: 1. Adding an abstract method "fly" into the class Animal. Then, I force the sub-classes should be implemented this method, something like: public abstract class Animal{ //bla bla public abstract void fly(); } public class Bird extends Animal{ //bla bla public void fly(){ System.out.println("Fly high"); } } public class Dog extends Animal{ //bla bla public void fly(){ System.out.println("Cant fly"); } } 2. Creating an interface with method "fly" inside. The same issue to an abstract class, I force the classes these implement this interface should have a method "fly" inside: public interface Flyable{ public void fly(); } public class Bird implements Flyable{ //bla bla public void fly(){ System.out.pr...

Merging source in SVN

My team has used Primefaces for our projects. We sometimes have several branches of the projects with a new Primefaces's release. For example, we currently have a project with two branches, a branch for using Primeface 4.0, a trunk for using Primeface 5.0, and we are working these parallel branches. Our project looks like the following: - myProject - branches + primefaces4 + tag + trunk (primefaces5) My problem is how to copy the same source from the trunk to the branch "primefaces4". That is where SVN Merging can help! Here is the steps those I have conducted in my project. Step 1 : open the project with the branch "primefaces4" Step 2 : Team > Merge... Chose the trunk's URL. For example: http://192.168.9.10/svn/myProject/trunk Step 3 : Select the revision from "trunk" to merge. For example: +--revision--+--date--------+--author----+--comment---+ + 10 + 03.10.2014 + vanhuong + f1: part 3 + + 9 ...

Validate date with Datejs

Datejs is an open source JavaScript Date library for parsing, formatting and processing. Website: http://www.datejs.com function isValid(date, pattern){ if(pattern == null){ return false; } var parseExact = Date.pareExact(date, pattern); if(parseExact !== null){ return true; } return false; } Another popular date library is Moment.js

Only allow input number value with autoNumeric.js

autoNumeric is a jQuery plugin that automatically formats currency and numbers as you type on form inputs. I used autoNumeric 1.9.21 for demo code. 1. Dowload autoNumeric.js file from https://github.com/BobKnothe/autoNumeric 2. Import to project <script src="http://ajax.googleapis.com/ajax/libs/jquery/1.11.0/jquery.min.js"></script> <script type="text/javascript" src="js/autoNumeric.js"></script> 3. Define a function to use it <script type="text/javascript"> /* only number is accepted */ function txtNumberOnly_Mask() { var inputOrgNumber = $("#numberTxt"); inputOrgNumber.each(function() { $(this).autoNumeric({ aSep : '', aDec: '.', vMin : '0.00' }); }); } </script> 4. Call the function by event <form> <input type="text" value="" id="numberTxt"/>(only number) </form> <script ty...

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