October 10, 2001 - Detecting An Event within A Page | WebReference

October 10, 2001 - Detecting An Event within A Page

Yehuda Shiran October 10, 2001
Detecting An Event within A Page
Tips: October 2001

Yehuda Shiran, Ph.D.
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Usually, you attach an event handler to a specific element on the page, such as an image, a text box, or a popup window. Sometimes, though, you want to attach an event handler to a group of elements. Instead of duplicating the attachment for all members of the group, you can attach the event handler to the containing page, and figure out during the event firing which element the event was fired on. When you want to catch an event within a page, you can use the attachEvent() method. The attachEvent() syntax is as follows:

  object.attachEvent(event, eventHandler);
If there is an additional event handler defined for the object the event fired on, it will be run before the function eventHandler() is called. If you attach several event handlers to the same page, they will be called in a random order, immediately after the object's event handler is run, if at all defined.

Let's take an example. In the page's init() function you can ask that the function mouseDownHandler() be called when the onmousedown event fires:

  document.attachEvent("onmousedown", mouseDownHandler);
And you can determine the object it fired on by going:

  objectClicked = event.srcElement.id;