;(function(designWidth, maxWidth) {
    var doc = document,
        win = window;
    var docEl = doc.documentElement;
    var tid;
    var rootItem,rootStyle;

    function refreshRem() {
        var width = docEl.getBoundingClientRect().width;
        if (!maxWidth) {
            maxWidth = 540;
        };
        if
 
 (width > maxWidth) {
            width = maxWidth;
        }
        //與淘寶做法不同，直接採用簡單的rem換算方法1rem=100px
        var rem = width * 100 / designWidth;
        //相容UC開始
        rootStyle="html{font-size:"+rem+'px !important}';
        rootItem = document.getElementById('rootsize') || document.createElement("style"
 
);
        if(!document.getElementById('rootsize')){
        document.getElementsByTagName("head")[0].appendChild(rootItem);
        rootItem.id='rootsize';
        }
        if(rootItem.styleSheet){
        rootItem.styleSheet.disabled||(rootItem.styleSheet.cssText=rootStyle)
        }else{
        try
 
{rootItem.innerHTML=rootStyle}catch(f){rootItem.innerText=rootStyle}
        }
        //相容UC結束
        docEl.style.fontSize = rem + "px";
    };
    refreshRem();

    win.addEventListener("resize", function() {
        clearTimeout(tid); //防止執行兩次
        tid = setTimeout(refreshRem, 300);
    }, false);

    win.addEventListener("pageshow", function(e) {
        if (e.persisted) { // 瀏覽器後退的時候重新計算
            clearTimeout(tid);
            tid = setTimeout(refreshRem, 300);
        }
    }, false);

    if (doc.readyState === "complete") {
        doc.body.style.fontSize = "16px";
    } else {
        doc.addEventListener("DOMContentLoaded", function(e) {
            doc.body.style.fontSize = "16px";
        }, false);
    }
})(640, 640);