The mouse’s position is reported on the event object received by a handler for the mousemove event, which you can attach to the window (the event bubbles):
(function() {
document.onmousemove = handleMouseMove;
function handleMouseMove(event) {
var eventDoc, doc, body;
event = event || window.event; // IE-ism
// If pageX/Y aren’t available and clientX/Y are,
// calculate pageX/Y – logic taken from jQuery.
// (This is to support old IE)
if (event.pageX == null && event.clientX != null) {
eventDoc = (event.target && event.target.ownerDocument) || document;
doc = eventDoc.documentElement;
body = eventDoc.body;
event.pageX = event.clientX +
(doc && doc.scrollLeft || body && body.scrollLeft || 0) –
(doc && doc.clientLeft || body && body.clientLeft || 0);
event.pageY = event.clientY +
(doc && doc.scrollTop || body && body.scrollTop || 0) –
(doc && doc.clientTop || body && body.clientTop || 0 );
}
// Use event.pageX / event.pageY here
}
})();
(Note that the body of that if will only run on old IE.)
Example of the above in action – it draws dots as you drag your mouse over the page. (Tested on IE8, IE11, Firefox 30, Chrome 38.)
If you really need a timer-based solution, you combine this with some state variables:
(function() {
var mousePos;
document.onmousemove = handleMouseMove;
setInterval(getMousePosition, 100); // setInterval repeats every X ms
function handleMouseMove(event) {
var dot, eventDoc, doc, body, pageX, pageY;
event = event || window.event; // IE-ism
// If pageX/Y aren’t available and clientX/Y are,
// calculate pageX/Y – logic taken from jQuery.
// (This is to support old IE)
if (event.pageX == null && event.clientX != null) {
eventDoc = (event.target && event.target.ownerDocument) || document;
doc = eventDoc.documentElement;
body = eventDoc.body;
event.pageX = event.clientX +
(doc && doc.scrollLeft || body && body.scrollLeft || 0) –
(doc && doc.clientLeft || body && body.clientLeft || 0);
event.pageY = event.clientY +
(doc && doc.scrollTop || body && body.scrollTop || 0) –
(doc && doc.clientTop || body && body.clientTop || 0 );
}
mousePos = {
x: event.pageX,
y: event.pageY
};
}
function getMousePosition() {
var pos = mousePos;
if (!pos) {
// We haven’t seen any movement yet
}
else {
// Use pos.x and pos.y
}
}
})();
As far as I’m aware, you can’t get the mouse position without having seen an event, something which this answer to another Stack Overflow question seems to confirm.
Side note: If you’re going to do something every 100ms (10 times/second), try to keep the actual processing you do in that function very, very limited. That’s a lot of work for the browser, particularly older Microsoft ones. Yes, on modern computers it doesn’t seem like much, but there is a lot going on in browsers… So for example, you might keep track of the last position you processed and bail from the handler immediately if the position hasn’t changed.
onmousemove = function(e){console.log(“mouse location:”, e.clientX, e.clientY)}
Open your console (Ctrl+Shift+J), copy-paste the code above and move your mouse on browser window.