手机适配（单独引入就可用）

(function(doc,win){var docEl=doc.documentElement,resizeEvt='orientationchange'in window?'orientationchange':'resize',recalc=function(){var clientWidth=docEl.clientWidth;if(!clientWidth){return}if(clientWidth>=750){docEl.style.fontSize='100px'}else{docEl.style.fontSize=100*(clientWidth/750)+'px'}};if(!doc.addEventListener){return}win.addEventListener(resizeEvt,recalc,false);doc.addEventListener('DOMContentLoaded',recalc,false)})(document,window);

(function (doc, win) {
    var docEl = doc.documentElement,
        resizeEvt = 'orientationchange' in window ? 'orientationchange' : 'resize',
        recalc = function () {
            var clientWidth = docEl.clientWidth;
            if (!clientWidth) return;
            if(clientWidth>=750){
              // 这里的750 取决于设计稿的宽度
                docEl.style.fontSize = '100px';
            }else{
                docEl.style.fontSize = 100 * (clientWidth / 750) + 'px';
            }
        };

    if (!doc.addEventListener) return;
    win.addEventListener(resizeEvt, recalc, false);
    doc.addEventListener('DOMContentLoaded', recalc, false);
})(document, window);