function getScrollWidth() {

    var noScroll, scroll, oDiv = document.createElement('div');

    oDiv.style.cssText = 'position:absolute; top:-1000px;     width:100px; height:100px; overflow:hidden;';

    noScroll = document.body.appendChild(oDiv).clientWidth;

    oDiv.style.overflowY = 'scroll';

    scroll = oDiv.clientWidth;

    document.body.removeChild(oDiv);

    return noScroll-scroll;

}

alert(getScrollWidth()); //chrome下是15，其余的为17