/**
 * rem计算方式：设计图尺寸px / 100 = 实际rem  例: 100px = 1rem
 */
!function (window) {

    /* 设计图文档宽度 */
    var docwidth = 750;

    var doc = window.document,
        docel = doc.documentelement,
        resizeevt = 'orientationchange' in window ? 'orientationchange' : 'resize';

    var recalc = (function refreshrem () {
        var clientwidth = docel.getboundingclientrect().width;

        /* 8.55：小于320px不再缩小，20：大于750px不再放大 */
        docel.style.fontsize = math.max(math.min(20 * (clientwidth / docwidth), 20), 8.55) * 5 + 'px';

        return refreshrem;
    })();

    /* 添加倍屏标识，安卓倍屏为1 */
    docel.setattribute('data-dpr', window.navigator.appversion.match(/iphone/gi) ? window.devicepixelratio : 1);

    if (/ip(hone|od|ad)/.test(window.navigator.useragent)) {
        /* 添加ios标识 */ 
        doc.documentelement.classlist.add('ios');
        /* ios8以上给html添加hairline样式，以便特殊处理 */
        //if (parseint(window.navigator.appversion.match(/os (\d+)_(\d+)_?(\d+)?/)[1], 10) >= 8)
            //doc.documentelement.classlist.add('hairline');
    }

    if (!doc.addeventlistener) return;
    window.addeventlistener(resizeevt, recalc, false);
    doc.addeventlistener('domcontentloaded', recalc, false);

}(window);