兼容IE的getBoundClientRect

get-bounding-rect.js

function getRect (element) {
    var rect = element.getBoundingClientRect();
    var top = document.documentElement.clientTop;
    var left= document.documentElement.clientLeft;
    return{
        top : rect.top - top,
        bottom : rect.bottom - top,
        left : rect.left - left,
        right : rect.right - left
    }
}