What is the EVALUATE Statement used for? How does it work?

When there are multiple options to choose from, the EVALUATE statement works best. When there are several choices to be made, IF-ELSE logic can become very complicated. To avoid writing complex nested IF Conditionals(condition-within-condition), the EVALUATE Statement can be used. The EVALUATE statement is the COBOL equivalent of switch-case in most conventional programming languages.

The general format of the EVALUATE Statement is as follows :

Syntax:

EVALUATE
   WHEN condition-1
     Statement-1
     ...

   WHEN condition-2
     Statement-2
     ...

   WHEN OTHER
     Statement-n
     ...
END-EVALUATE
STATEMENT-X

Interpretation:

The EVALUATE computes the value of the main expression.

1. If the value satisfies condition-1, then Statement-1 is performed, and after execution, control jumps to STATEMENT-X(Outside the EVALUATE Block).

2. Else If the value satisfies condition-2, then Statement-2 is performed, and after execution, control jumps to STATEMENT-X(Outside the EVALUATE Block).

...

n. If the values satisfies none of the above conditions, then by default WHEN OTHER case is executed(Statement-n), and then the control jumps to STATEMENT-X.(Outside the EVALUATE Block)

Thus, at each level of the EVALUATE block, the condition is checked, if it holds true, the case is executed, if it doesn’t hold true, you descend to the next lower level and so on... This is called a fall-through.

Example:

 
Upon running the above COBOL Program, you should get the following output-

How to Develop a JQuery plugin easily

jQuery is the most popular JavaScript library and many sites adopt it for dynamic effects and Ajax functionality. However, relatively few developers delve into the depths of plugin development.

Why a plugin?

First of all, you might ask yourself why you'd want to develop a plugin. The first and best reason is the ability to maintain chainability. When people ask me the best feature of jQuery, I'd probably mention the chainability. It allows you do do things like:

Code:

$('.className').addClass('enabled').append('Click here').click( func );

This would take every element with a class name of 'className', add a new class name to it, append some HTML, and set a click event handler. When you develop a plugin, you have the ability to intject your own functionality while still maintaining the chain.Another reason to develop a jQuery plugin is simply to be consistent with the jQuery ethos. The jQuery ethos, in my opinion, is that the HTML element is king (or queen — lest I be mysoginistic about my HTML elements). It's all about getting elements and then performing actions on those elements.Now, let's take a look at how to create a plugin, of which there are two possible approaches.

Approach 1: The Function

jQuery.log = function(message) { if(window.console) { console.debug(message); } else { alert(message); } };

In this example, a log function has been attached to the jQuery object. You can then call this in your code using jQuery.log('my message') or $.log('my message'). There's no chainability or HTML elements involved (unless you add that into your code).

Approach 2:

jQuery.fn.newMethod = function(){ return this; }

The this keyword refers to the current jQuery object. You'll have access to jQuery's methods and functions. If you need to perform an action on each element then you can do something like this:

jQuery.fn.newMethod = function(){
    return this.each(function(){
        alert(this);
    });
}
The this keyword within the inner function refers to the current HTML element, which won't have access to the jQuery methods (although, it's as easy as wrapping it in the jQuery object to get those methods back).
Don't use $
When developing a plugin, you'll want to avoid using the familiar dollar function, $, to avoid any conflicts. jQuery has a no-conflict mode for turning the alias on and off. If you want, you can alias the jQuery function within your plugin. It'll be self-contained and avoid any outside conflicts.