The ctrlKey event attribute returns a Boolean value that indicates whether or not the "Ctrl" key was pressed when an event was triggered. The following example shows that how we can do this
<html>
<head>
<script type="text/javascript">
function iskeypress(event)
{
if (event.ctrlKey==1)
{
alert("The Ctrl key is pressed now you may continue....")
}
else
{
alert("OOps The Ctrl key is not pressed")
}
}
</script>
</head>
<body onmousedown="iskeypress(event)">
</body>
</html>
There are lots of event attribute we can use it here like altKey,shiftKey,metaKey...