Event object in Javascript, trouble finding information -

i believe there object in javascript called event, see in code wasn't written me in lines this:

event.x + document.body.scrollleft; 

i having trouble finding more out information, furthermore, object comes undefined in firefox. works fine in other browsers. can provide me more information? how access object in firefox?

official w3c reccomendation

clientx , clienty official event property handlers looking for. although might want consider screenx , screeny too.

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events (api)

events

creating, triggering events

event handlers

orientation , motion data

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window event x , y property

explanation

event.x , event.y, those?

first of all, x , y properties not in events. relative on event triggered.

here example:

document.body.onclick = function(){console.log(window.event.x)}; 

if paste , execute code in browser's console, log x position of cursor each time click.

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although taking @ example:

document.body.onkeyup = function(){console.log(window.event.x)}; 

the console log undefined each , everytime release key keyboard, since onkeyup() event not hold values x , y properties.