js獲取瀏覽器滾動條寬度

function getScrollbarWidth() {
        var oP = document.createElement('p'), styles = {
            width: '100px',
            height: '100px',
            overflowY: 'scroll',
        }, i, scrollbarWidth;

        for (i in styles){
            oP.style[i] = styles[i];
        }
        document.body.appendChild(oP);
        scrollbarWidth = oP.offsetWidth - oP.clientWidth;
        oP.remove();

        return scrollbarWidth;
    }