January 1, 2001 - The Netscape 6 Event Listener

Yehuda Shiran January 1, 2001
The Netscape 6 Event Listener
Tips: January 2001

Yehuda Shiran, Ph.D.
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Netscape 6 introduced a new event concept, the event listener. You attach an event listener to an object. The event listener listens for a specified event, and when the event occurs, the event listener executes a pre-specified action. You can define several event listeners for the same object, and for the same event type. For example, two separate event listeners can listen to a click event for a specific button, and execute two different actions. You add an event listener by the addEventListener() method:

object.addEventListener(eventType, functionCall, downBool)
where:

eventType is the type of the event you want to listen to. Do not include the "on" prefix. Examples: "mouseover", "click", "mouseout", "mouseup", and "mousedown".
  • functionCall is the function you want to execute when the event is detected. This is the actual function reference and not a string, so don't include the function name in quotes. If you need to pass parameters to the function, simply pass them in this call, as functionName(param1, param2).
  • downBool is a Boolean variable (true or false) that tells the listener on which phase to intercept the event. A true value asks the listener to intercept the event on its way down from the browser window object to its target object (capture phase). A false value signals the listener to intercept it on its way up from the target object to the window object (bubbling phase).