TypeScript is now a very popular language to create typed JavaScript code to reduce development error. It provides a type system on top of JavaScript which has only a weak type system. Once the TypeScript code is developed, it can be compiled into corresponding JavaScript so that they can be loaded and parsed by browser.Webpack is another tool for bundling multiple JS files into a single one so that no multiple connections to be established between browser and server. when a page is loaded This would reduce the bandwidth consumption and improve website performance in general.These two are good...

In our daily work, there might be mistakes made which got some data or even databases deleted in MySQL. If this happens on production, it would be a nightmare. In case this happens, normally DBA would jump in to save the world. And they would try to recover the data from the backup if there is any. But if there is no backup, then the show stops.Hence database backup is necessary on production environments to avoid such awkward situation. Also normally in MySQL, binlog should be enabled as well in ROW mode so that recovery can be replayed starting from the backup time point to the incident time...

Sometimes when handling a long running process, there would be need to track the progress so that people know something is still running instead of doubting something goes wrong. In this case, a progress bar which indicates the current status and progress would be desired.This post will show an example on how to implement progress bar using GoLang. Let's take a look at the final outcome first before jumping into the implementation detail.The key in the implementation is actually just the \r control flag for fmt.Printf(). \r is actually the carriage return control which tells the cursor to move...

A certificate is often used to prove the identity of a server. The certificate will contain information such as the subject and issuer of the certificate. It will also contain the validation date of the certificate. A certificate is often exported to an external cert file which is transferred over the internet. We will often see its use in SSL communication which provides secure communication between two entities.In this post, we will show how to read the data from an external certificate file and generate a X509 certificate object with the data. This object can then be used to conduct other o...

JKS is Java Keystore, a proprietary keystore type designed for Java. It can be used to store private keys and certificates used for SSL communication, it cannot store secret keys however. The keytool shipped with JDKs cannot extract private keys stored on JKS. This type of keystore usually has an extension of jks.Next we will show how to operate the JKS keystore with pure Java code.Create JKS keystoreThe simplest method to create a JKS keystore to create an empty keystore. We can first get an instance of KeyStore and then load a null keystore. After loading the null keystore, we just need to c...

When we access one website, the site usually should have a mechanism to keep track of the status of the user on the site. There are a few mechanisms supported by many server side languages to help track user status such as session and cookie.Today we will talk about session, when creating a session, we need to keep track of many data, besides user data, we also need to tell the server what is the timeout of the session so that we can garbage collect the session data which should not be stored anymore. How do we implement a reliable session mechanism?In PHP, we are often told that we can change...

Have you ever thought about writing extension for web browsers so that we can complete some tasks easily. Do you think writing extension for browsers is very difficult? You have no clue where to begin? On Chrome, this isn't any problem now as long as you know how to write HTML,CSS and JavaScript.We will show one example of Chrome extension today. The extension will display a desktop notification on your desktop. You need to create two files here, one is the notification.json which is the configuration file for the extension, it contains the name and version and some initialization information ...

These two days, I am building a website and deploying it on a VPS server which uses CentOS 5. I don't have cPanel or Plesk for my account, so I need to install and configure everything myself including Apache, PHP, MySQL and FTP server, also today's topic cron job. Since my website has a ranking algorithm to calculate the rankings of each link and update the ranking on database and I need to calculate the rankings every 5 minutes, so I think to use cron jobs. Here are what I have done which may help you.First we need to understand the crontab commands, it can have different options with this c...