Question

I’m helping to debug a website and sometimes i get this error :
Object required on CWS.js line 45 character 3

// Track cursor position
var CWS_curPosX, CWS_curPosY;
document.onmousemove = CWS_MouseMove;

function CWS_MouseMove(evt)
{

if(window.Event)
{
    if(evt && evt.pageX)
    {
        CWS_curPosX = evt.pageX;
        CWS_curPosY = evt.pageY; 
    }
}
else
{
    CWS_curPosX = event.clientX + document.body.scrollLeft; // line 45
    CWS_curPosY = event.clientY + document.body.scrollTop;
}

I have no idea to solve this…
Thanks in advance.

Answer 1

There is a couple of crucial isues with your code, primarily your use of window.Event – this if(...) condition will always evaluate false, as no browser supports this property on the window object. In actual fact the property has a lower case e in IE.

So this construct is often used, and looks similar to yours:

function someEventHandler(evt){
   if(window.event){ // Note lower case 'e' in 'event'
       // browser is IE, read properties of the event from window.event
   }
   else{
       // browser is probably some flavour of Mozilla, use the passed-in 'evt' 
       // parameter to read properties of the event
   }
}

Read this link (event object in different browsers) for more info.

This cross-browser difference is one of many reasons many people tend to use a framework such as jQuery which simplifies this event-handling code into one unified method of reading properties of the event.