(function(win) {//计算自适应html元素的font-size大小的方法
    var doc = win.document;
    var docEl = doc.documentElement;
    var tid;
    function refreshRem() {
        var width = docEl.getBoundingClientRect().width;
        if(width >= 750) width = 750;
        if(width <= 320) width = 320;
        var rem = width / 7.5;
        docEl.style.fontSize = rem + 'px';
    }
    win.addEventListener('resize', function() {
        clearTimeout(tid);
        tid = setTimeout(refreshRem, 300);
    }, false);
    refreshRem();
})(window);