JS instance method to obtain mouse coordinates_javascript skills

var restrictX;
var restrictY;
var tip;
// Mouse coordinates
function mousePosition(ev) {
return {
x : ev.clientX document.documentElement.scrollLeft - document.documentElement.clientLeft,
y : ev.clientY document .documentElement.scrollTop - document.documentElement.clientTop
};
}
// Mouse event
function mouseMove(ev) {
ev = ev || window.event;
var mousePos = mousePosition(ev);
restrictX = mousePos.x;
restrictY = mousePos.y;
}
document.onmousemove = mouseMove;
document.onclick = mouseMove;

var restrictX;
var restrictY;
var tip;
// Mouse coordinates
function mousePosition(ev){
var scrollLeft = document.documentElement.scrollLeft || document.body.scrollLeft;
var scrollTop = document.documentElement.scrollTop || document.body.scrollTop;
return {
x:ev.clientX scrollLeft - document.documentElement.clientLeft,
y:ev.clientY scrollTop - document.documentElement.clientTop
};
}
// Mouse event
function mouseMove(ev){
ev = ev || window.event;
var mousePos = mousePosition(ev);
restrictX = mousePos.x;
restrictY = mousePos.y;
}
document.onmousemove = mouseMove;
document.onclick = mouseMove;

var scrollLeft = document.documentElement.scrollLeft || document.body.scrollLeft;
var scrollTop = document.documentElement.scrollTop || document.body.scrollTop;