ios 浏览器内容较少时隐藏地址栏

　　　　　　window.onload = function() {
                scroll();
            }

            function scroll() {
                if(document.documentElement.scrollHeight <= document.documentElement.clientHeight) {
                    bodyTag = document.getElementsByTagName('body')[0];
                    bodyTag.style.height = document.documentElement.clientWidth / screen.width * screen.height + 'px';
                }
            }