Technical Notes

Implementing printing functionality on web pages using JavaScript's window.print() function allows users to print the current page directly from the browser. Implementing Print Functionality To enable printing, simply use a button with an onclick event: <input type="button" value="Print" onclick="window.print()" /> This button, when clicked, triggers the browser's print dialog. Making a Page Printer-Friendly A printer-friendly page is optimized for printing, usually with minimal graphics and ads: Create a separate printer-friendly version of the page without unnecessary elements. Alternatively, mark printable content with HTML comments like <!-- PRINT STARTS HERE --> and <!-- PRINT ENDS HERE --> , and use server-side scripts to generate a printable version. Our site follows these practices to provide a better printing e...

In traditional web forms, validation occurred on the server after submission, leading to delays and server load. JavaScript allows for client-side form validation, checking data before it's sent to the server. Basic Form Validation Basic validation ensures required fields are filled and formats are correct: <form action="/cgi-bin/test.cgi" name="myForm" onsubmit="return validate()"> <input type="text" name="Name" /> <input type="text" name="EMail" /> <input type="text" name="Zip" /> <select name="Country"> <option value="-1" selected>[choose yours]</option> <option value="1">USA</option> <option value="2">UK</option> <option value="3">INDIA</option> </select> <input type="submit" val...

Errors in programming can be categorized into three types: Syntax Errors, Runtime Errors, and Logical Errors. Syntax Errors Syntax errors, also known as parsing errors, occur during compilation or interpretation: <script type="text/javascript"> window.print(; // Syntax error: missing closing parenthesis </script> When a syntax error occurs in JavaScript, only the affected thread stops, allowing other threads to continue. Runtime Errors Runtime errors, or exceptions, occur during script execution: <script type="text/javascript"> window.printme(); // Runtime error: calling a non-existing function </script> Exceptions affect the thread they occur in, but other JavaScript threads can continue normally. Logical Errors Logical errors are mistakes in the logic of your script, resulting in unexpected behavior: These errors are not sy...

GET vs POST Methods in HTTP Understanding GET and POST Methods in HTTP When it comes to web development, understanding the fundamental differences between the GET and POST methods in HTTP is essential. These methods are used to send data between the client and server, but they do so in distinct ways, each with its own advantages and limitations. Let's delve into the key differences between GET and POST methods. GET Method: Data Transmission: In the GET method, data is appended to the URL as query parameters. This makes it easily visible in the browser's address bar. Single Call System: GET requests are simple and involve a single call to the server. Data Size Limit: The amount of data that can be sent via GET is limited to around 256 characters due to URL length restrictions. Speed: Data transmission is generally faster with GET reque...

Setting Up Gzip Compression for Better Web Performance Compression is a simple, effective way to save bandwidth and speed up your site. I hesitated when recommending gzip compression for speeding up your JavaScript due to problems in older browsers. But it's the 21st century. Most of my traffic comes from modern browsers, and quite frankly, most of my users are fairly tech-savvy. I don't want to slow everyone else down because somebody is chugging along on IE 4.0 on Windows 95. Google and Yahoo use gzip compression. A modern browser is needed to enjoy modern web content and modern web speed — so gzip encoding it is. Here's how to set it up. Wait, wait, wait: Why are we doing this? Before we start, I should explain what content encoding is. When you request a file like http://www.yahoo.com/index.html , your browser talks to a web server. The conversation goes a little like this: ...

Servlet Lifecycle Overview Servlet Lifecycle Overview The life cycle of a servlet can be categorized into four parts: Loading and Instantiation: The servlet container loads the servlet during startup or when the first request is made. The loading of the servlet depends on the <load-on-startup> attribute in the web.xml file. If <load-on-startup> has a positive value, the servlet is loaded with the container; otherwise, it loads when the first request is made. After loading, the container creates instances of the servlet. Initialization: After creating the instances, the servlet container calls the init() method and passes the servlet initialization parameters to it. The init() method must be called before the servlet can service any requests. Initialization parameters persist until the servlet is destroyed. The init() method is called only once t...

Servlet Methods Overview Overview of Servlet Methods A Generic servlet contains the following five methods: init() public void init(ServletConfig config) throws ServletException The init() method is called only once by the servlet container throughout the life of a servlet. This method allows the servlet to initialize and be placed into service. The servlet cannot be put into service if: The init() method does not return within a fixed time set by the web server. It throws a ServletException. Parameters: The init() method takes a ServletConfig object containing initialization parameters and servlet configuration and throws a ServletException if an exception occurs. service() public void service(ServletRequest req, ServletResponse res) throws ServletExceptio...