get offset

offset.js

function getOffset (ele) {
    var box = ele.getBoundingClientRect();
    return {
        top: box.top + (window.pageYOffset || document.documentElement.scrollTop) - (document.documentElement.clientTop || 0),
        left: box.left + (window.pageXOffset || document.documentElement.scrollLeft) - (document.documentElement.clientLeft || 0)
    };
};