let flexible = (designWidth, maxWidth,minWidth) =>{
    var doc = document, win = window, docEl = doc.documentElement, remStyle = document.createElement("style"), tid;
    designWidth = designWidth || 1920;
    maxWidth = maxWidth || 2560;
    minWidth = minWidth || 1024;
    function refreshRem() {
        var width = docEl.getBoundingClientRect().width;
        var height = docEl.getBoundingClientRect().height;
        maxWidth = maxWidth || 1920;
		if(width/height>1.98) width = height * 1.98;
        width > maxWidth && (width = maxWidth);
        width < minWidth && (width = minWidth);
        var rem = width * 10 / designWidth;
		docEl.style.fontSize = rem+'px'
        remStyle.innerHTML = 'html{font-size:' + rem + 'px;}';
    }
    // if (docEl.firstElementChild) {
    //     docEl.firstElementChild.appendChild(remStyle);
    // } else {
    //     var wrap = doc.createElement("div");
    //     wrap.appendChild(remStyle);
    //     doc.write(wrap.innerHTML);
    //     wrap = null;
    // }
    //要等 wiewport 设置好后才能执行 refreshRem，不然 refreshRem 会执行2次；
    refreshRem();
    win.addEventListener("resize", function() {
        clearTimeout(tid); //防止执行两次
        tid = setTimeout(refreshRem, 300);
    }, false);

    win.addEventListener("pageshow", function(e) {
        if (e.persisted) { // 浏览器后退的时候重新计算
            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);
    }
};

export default flexible