Learn Prototype
Prototype Resources
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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]);
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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 :
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>
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To understand it in better way you can Try it yourself.
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