rem的使用和图片懒加载

每个页面都需要加

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

图片懒加载

//img设置一个自定义属性，用来放真是的img路径。用getAttribute获取自定义属性的值

 <script type="text/javascript">
   var aImg = document.querySelectorAll('img');
   var len = aImg.length;
   var n = 0;//存储图片加载到的位置，避免每次都从第一张图片开始遍历
   window.onscroll = function() {
      scroll_on();
   };
function scroll_on(){
     var seeHeight = document.documentElement.clientHeight;
     var scrollTop = document.body.scrollTop || document.documentElement.scrollTop;
     for (var i = n; i < len; i++) {
        if (aImg[i].offsetTop+500 < seeHeight + scrollTop) {
            // if (aImg[i].getAttribute('src') == '') {
                aImg[i].src = aImg[i].getAttribute('guoyu-src');
            // }
            n = i + 1;
            console.log('n = ' + n);
        }
    }
}
scroll_on();

</script>