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jsFiddle sample is available at http://jsfiddle.net/62Yuu/

It "console.log"s the "event.offestX" and "event.layerX". Firefox 4 prints something like "undefined 123" while chrome prints (in most cases) equal numbers for both values.

http://api.jquery.com/mousemove/

Properties such as .clientX, .offsetX, and .pageX are available, but support for them differs between browsers. Fortunately, jQuery normalizes the .pageX and .pageY properties so that they can be used in all browsers.

Does .pageX do what you expected?

Ok, not necessarily a bug. However, it would be pretty cool, if jQuery would normalize offestX as well (if possible) ;)

Every extra property that we have to normalize in an event handler is more time spent in the event handler. If .pageX doesn't do what you want then you're free to analyze the other browser-specific data and extract what you need from it.

Something in jquery doing this :

if (!evt.offsetX){
     evt.offsetX = evt.layerX - $(evt.target).position().left;
}
if (!evt.offsetY){
     evt.offsetY = evt.layerY - $(evt.target).position().top;
}

would be useful;

Just for clarification, in case anybody needs to get this functionality working (without modifying the core):

var offX, offY;
if (!(e.offsetX || e.offsetY)) {
	offX = e.layerX - $(e.target).position().left;
	offY = e.layerY - $(e.target).position().top;
}
else {
	offX = e.offsetX;
	offY = e.offsetY;
}

You can then use it like:

$('#example').css({
	left:  offX,
	top:   offY
});

(for example in a mousemove event)

please, add offsetX/Y for Firefox in Event object

I can't seems to find event.layerX however this code seems to work:

var offsetX = event.screenX - $(event.target).offset().left;

though chrome/firefox gives me slight different results (chrome give me 90 where firefox give me 94 in one case)

I use the approach below:

#!js
 var x = evt.offsetX;
 if (x == undefined) {
     x = evt.clientX - $(evt.target).offset().left;
 }

I don't think this justified a 'polyfill'. When I want offsetX for example, I just put this instead:

(ev.offsetX || ev.clientX - $(ev.target).offset().left)

This way it's slightly faster when already exists.

for offsetY, I suggest:

(ev.offsetY || ev.pageY - $(ev.target).offset().top)

erratum

(ev.offsetY || ev.pageY - $(ev.target).offset().top)

DominiqueF is right, pageX and pageY is the mouse position relative to the left and top edge of the document. OffsetX and offsetY are relative to the target element, so it's just a matter of taking the difference between absolute mouse offset and target offset.

Play nice, perform typeof check instead of truthy check since offsetX may be defined with zero. Also, cache your object lookup.

if(typeof event.offsetX === "undefined" || typeof event.offsetY === "undefined") {

var targetOffset = $(event.target).offset();

event.offsetX = event.pageX - targetOffset.left;

event.offsetY = event.pageY - targetOffset.top;

}

erratum is right

if(typeof event.offsetX === "undefined" || typeof event.offsetY === "undefined") {
   var targetOffset = $(event.target).offset();
   event.offsetX = event.pageX - targetOffset.left;
   event.offsetY = event.pageY - targetOffset.top;
}

#11951 is a duplicate of this ticket.

#12007 is a duplicate of this ticket.