Onmouseover child div problem and event bubbling

Question

I have a small div above (hover) a big one.
I assign onmouseover and onmouseout events to the wrapper div.
For image caption roll-over animation.

The proble

Answer 1

This article on quirksmode ( near the bottom ) has an explanation of what you are experiencing and a script that might help you. There is a lot of cross browser info regarding mouse events too

OK, here's some working code. I don't promise this is the most efficient or that it won't cause memory leaks in IE (or that it works in IE - please let me know ). This is why people use libraries, much safer and easier.

// a general purpose, cross browser event adder
// returns a function that if run removes the event
function addEvent( el, eventType, handler, capturing ) {
    if( el.addEventListener ) {
        el.addEventListener( eventType, handler, capturing || false );
        var removeEvent = function() { el.removeEventListener( eventType, handler, capturing || false ) };
    } else if( el.attachEvent ) {
        var fn = function() {
            handler.call( el, normalise( window.event ) );
        };
        el.attachEvent( 'on'+eventType, fn );
        var removeEvent = function(){ el.detachEvent( 'on'+eventType, fn ) };
    }
    function normalise( e ) {
        e.target = e.srcElement;
        e.relatedTarget = e.toElement;

        e.preventDefault = function(){ e.returnValue = false };
        e.stopPropagation = function(){ e.cancelBubble = true };
        return e;
    };
    return removeEvent;
};



// adds mouseover and mouseout event handlers to a dom element
// mouseover and out events on child elements are ignored by this element
// returns a function that when run removes the events
// you need to send in both handlers - an empty function will do
function addMouseOverOutEvents( element, overHandler, outHandler ) {

    function out( e ) {
        var fromEl = e.target;
        var toEl = e.relatedTarget;
        // if the mouseout didn't originate at our element we can ignore it
        if( fromEl != element ) return;
        // if the element we rolled onto is a child of our element we can ignore it
        while( toEl  ) {
            toEl = toEl.parentNode;
            if( toEl == element ) return;
        }
        outHandler.call( element, e );
    }

    function over( e ) {
        var toEl = e.target;
        var fromEl = e.relatedTarget;
        // if the mouseover didn't originate at our element we can ignore it
        if( toEl != element ) return;
        // if the element we rolled from is a child of our element we can ignore it
        while( fromEl  ) {
            fromEl = fromEl.parentNode;
            if( fromEl == element ) return;
        }
        overHandler.call( element, e );
    }

    var killers = [];
    killers.push( addEvent( element, 'mouseover', over ) );
    killers.push( addEvent( element, 'mouseout', out ) );
    return function() {
        killers[0]();
        killers[1]();
    }
}

Example of use:

// add the events
var remover = addMouseOverOutEvents(
    document.getElementById( 'elementId' ),
    function( e ) {
        this.style.background = 'red';
        console.log( 'rolled in: '+e.target.id );
    },
    function( e ) {
        this.style.background = 'blue'
        console.log( 'rolled out: '+e.target.id );
    }    
);

//remove the events
remover();