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# Prototype Event observe() Method

This method registers an event handler on a DOM element.

To register a function as an event handler, the DOM element that you want to observe must already exist in the DOM

## Syntax:

    Event.observe(element,eventName,handler[,useCapture=false]);

Here is explanation about passed parameters:

- element: The DOM element you want to observe; as always in Prototype, this can be either an actual DOM reference, or the ID string for the element.

- evenetName: The standardized event name, as per the DOM level supported by your browser. This includes click, mousedown, mouseup, mouseover, mousemove and mouseout.

- handler: This is the event handler function. This can be an anonymous function you create on-the-fly.

- useCapture: Optionally, you can request capturing instead of bubbling. The details are in the DOM Level 2 Events

## Return Value :

- NA

## Example:

Here is an example which observe click event and take an action whenever a click event occurs.

    <html>
    <head>
    <title>Prototype examples</title>
       <script type="text/javascript"
       src="/javascript/prototype.js">
       </script>

    <script>

    // Register event 'click' and associated call back.
    Event.observe(document, 'click', respondToClick);

    // Callback function to handle the event.
    function respondToClick(event) {
      alert("You pressed the button...." );
    }

    </script>
    </head>

    <body>

       <p id="note"> Click anywhere to see the result.</p>

       <p id="para1">This is paragraph 1</p>
       <p id="para2">This is paragraph 2</p>

       <div id="division">
           This is divsion.
       </div>

    </body>
    </html>

To understand it in better way you can Try it yourself.

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