(function(win, mainw) {
    var doc = win.document; //当前文档对象
    var docEl = doc.documentElement; //文档对象根元素的只读属性
    var width1 =  docEl.getBoundingClientRect().width;
    var width2 =  document.documentElement.clientWidth;
    var width3 =  window.screen.availWidth;
    var minScreenWidth=width1<width2?width1:width2;
    minScreenWidth=minScreenWidth<width3?minScreenWidth:width3;
    //alert("width1: "+width1+" width2:"+width2+" width3:"+width3+" minScreenWidth: "+ minScreenWidth);
    var scale = minScreenWidth/ mainw;
    //alert("scale: "+ scale);
    //添加meta标签，设置name为viewport，content根据scale设置缩放比(默认、最大、最小缩放比)
    var metaEl = doc.createElement('meta');
    metaEl.setAttribute('name', 'viewport');
    //metaEl.setAttribute('content', 'width=device-width, initial-scale=' + scale + ', maximum-scale=' + scale + ', minimum-scale=' + scale + ', user-scalable=yes');
    metaEl.setAttribute('content', 'width=device-width, initial-scale=' + scale + ', maximum-scale= 1.0, minimum-scale= 0.1, user-scalable=yes');
    if (docEl.firstElementChild) {
        docEl.firstElementChild.appendChild(metaEl);
    } else {
        var wrap = doc.createElement('div');
        wrap.appendChild(metaEl);
        doc.write(wrap.innerHTML);
    }
})(window, 1200);