- Prototype Tutorial
- Prototype - Home
- Prototype - Short Overview
- Prototype - Useful Features
- Prototype - Utility Methods
- Prototype - Element Object
- Prototype - Number Processing
- Prototype - Strings Processing
- Prototype - Array Processing
- Prototype - Hash processing
- Prototype - Basic Object
- Prototype - Templating
- Prototype - Enumerating
- Prototype - Event Handling
- Prototype - Form Management
- Prototype - JSON Support
- Prototype - AJAX Support
- Prototype - Expressing Ranges
- Prototype - Periodical Execution
- Prototype Useful Resources
- Prototype - Quick Guide
- Prototype - Useful Resources
- Prototype - Discussion
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 are the explanations about the 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 http://www.w3.org/TR/DOM-Level-2Events/events.html.
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>