移动端屏幕尺寸自适应

var metaEl = document.querySelector('meta[name="viewport"]');
    var scale;
    scale = document.documentElement.clientWidth / 320;
    metaEl.setAttribute("content", "width=320,initial-scale=" + scale + ",maximum-scale=" + scale + ",user-scalable=no");
    var ispc = function() {
            var userAgentInfo = navigator.userAgent;
            var Agents = ["Android", "iPhone", "SymbianOS", "Windows Phone", "iPad", "iPod"];
            var flag = true;
            for (var v = 0; v < Agents.length; v++) {
                if (userAgentInfo.indexOf(Agents[v]) > 0) {
                    flag = false;
                    break
                }
            }
            return flag
        };