standardBoundingBox.js

/**
 * support for `Element.getBoudingClientRect()` goes back to IE5, FF3, and Chrome 1
 * it's great for getting the placement of a DOM element
 * it is supposed to include `top`, `bottom`, `left`, and `right` in browser coordinates
 * newer browsers also return `width` and `height`
 * this code patches that, allowing all browsers access to the `widht` and `height`
 */
function standardizeBoundingBox(bb) {
    //IE8 does not have width and height in bounding boxes
    return {
        width: bb.width || (bb.right - bb.left),
        height: bb.height || (bb.bottom - bb.top),
        top: bb.top,
        bottom: bb.bottom,
        left: bb.left,
        right: bb.right
    };
}

//usage
var el = document.getElementById('myElement');
var boundingBox = standardizeBoundingBox( el.getBoundingClientRect() );