移动端设置根节点字体大小

 var view_width = window.screen.availWidth;
            var _html = document.getElementsByTagName('html')[0];

            console.log(view_width)

            if (view_width > 750){
                _html.style.fontSize = 750 / 15 + 'px';
            }else{
                _html.style.fontSize = view_width / 15 + 'px';
            } var view_width = window.screen.availWidth;