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    Comparison of Event Targets

    This article is in need of a technical review.

    Event targets

    It's easy to get confused about which target to examine when writing an event handler. This article should clarify the use of the target properties.

    There are 5 targets to consider:

    Property Defined in Purpose
    event.target DOM Event Interface

    The DOM element on the lefthand side of the call that triggered this event, eg:

    element.dispatchEvent(event)
    
    event.currentTarget DOM Event Interface The EventTarget whose EventListeners are currently being processed. As the event capturing and bubbling occurs this value changes.
    event.relatedTarget DOM MouseEvent Interface Identifies a secondary target for the event.
    event.explicitOriginalTarget nsIDOMNSEvent.idl If the event was retargeted for some reason other than an anonymous boundary crossing, this will be set to the target before the retargeting occurs. For example, mouse events are retargeted to their parent node when they happen over text nodes (bug 185889), and in that case .target will show the parent and .explicitOriginalTarget will show the text node.
    Unlike .originalTarget, .explicitOriginalTarget will never contain anonymous content.
    event.originalTarget nsIDOMNSEvent.idl The original target of the event, before any retargetings. See Anonymous Content#Event_Flow_and_Targeting for details.

    Use of explicitOriginalTarget and originalTarget

    TODO: Only available in a Mozilla-based browser? TODO: Only suitable for extension-developers?

    Examples

    <!DOCTYPE html>
    <html>
    <head>
        <meta charset="utf-8">
        <meta http-equiv="X-UA-Compatible" content="IE=edge">
        <title>Comparison of Event Targets</title>
        <style>
            table {
                border-collapse: collapse;
                height: 150px;
                width: 100%;
            }
            td {
                border: 1px solid #ccc;
                font-weight: bold;
                padding: 5px;
                min-height: 30px;
            }
            .standard {
                background-color: #99ff99;
            }
            .non-standard {
                background-color: #902D37;
            }
        </style>
    </head>
    <body>
        <table>
        <thead>
            <tr>
                <td class="standard">Original target dispatching the event <small>event.target</small></td>
                <td class="standard">Target who's event listener is being processed <small>event.currentTarget</small></td>
                <td class="standard">Identify other element (if any) involved in the event <small>event.relatedTarget</small></td>
                <td class="non-standard">If there was a retargetting of the event for some reason <small> event.explicitOriginalTarget</small> contains the target before retargetting (never contains anonymous targets)</td>
                <td class="non-standard">If there was a retargetting of the event for some reason <small> event.originalTarget</small> contains the target before retargetting (may contain anonymous targets)</td>
            </tr>
        </thead>
        <tr>
            <td id="target"></td>
            <td id="currentTarget"></td>
            <td id="relatedTarget"></td>
            <td id="explicitOriginalTarget"></td>
            <td id="originalTarget"></td>
        </tr>
    </table>
    <p>Clicking on the text will show the difference between explicitOriginalTarget, originalTarget and target</p>
    <script>
        function handleClicks(e) {
            document.getElementById('target').innerHTML = e.target;
            document.getElementById('currentTarget').innerHTML = e.currentTarget;
            document.getElementById('relatedTarget').innerHTML = e.relatedTarget;
            document.getElementById('explicitOriginalTarget').innerHTML = e.explicitOriginalTarget;
            document.getElementById('originalTarget').innerHTML = e.originalTarget;
        }
    
        function handleMouseover(e) {
            document.getElementById('target').innerHTML = e.target;
            document.getElementById('relatedTarget').innerHTML = e.relatedTarget;
        }
    
        document.addEventListener('click', handleClicks, false);
        document.addEventListener('mouseover', handleMouseover, false);
    </script>
    </body>
    </html>

    Use of target and relatedTarget

    The relatedTarget property for the mouseover event holds the node that the mouse was previously over. For the mouseout event, it holds the node that the mouse moved to.

    Event type event.target event.relatedTarget
    mouseover the EventTarget which the pointing device entered the EventTarget which the pointing device exited
    mouseout the EventTarget which the pointing device exited the EventTarget which the pointing device entered

    TODO: Also needs descriptions about dragenter and dragexit events.

    Example

    <hbox id="outer">
      <hbox id="inner"
            onmouseover="dump('mouseover ' + event.relatedTarget.id + ' > ' + event.target.id + '\n');"
            onmouseout="dump('mouseout  ' + event.target.id + ' > ' + event.relatedTarget.id + '\n');"
            style="margin: 100px; border: 10px solid black; width: 100px; height: 100px;" />
    </hbox>
    

     

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    Last updated by: MHasan,