页面加载自动生成meta标签，做屏幕自适应功能

/**
*
* viewport scale根据设备像素比自动生成
* Html根元素font-size根据设备像素比自动生成
* by MC
*/

(document.DOMContentLoaded = function () {
var meta = document.createElement("meta"),
scale = 1.0 / window.devicePixelRatio;
meta.name = "viewport";
meta.content = "target-densitydpi=device-dpi,width=device-width,minimum-scale=" + scale + ",maximum-scale=" + scale + ",initial-scale=" + scale + ",user-scalable=no";
document.head.appendChild(meta);
document.documentElement.setAttribute("style", "font-size:" + 16 * window.devicePixelRatio + "px");
})();