移动端meta标签的设置

var phoneWidth = parseInt(window.screen.width);
var phoneScale = phoneWidth / 640;
var ua = navigator.userAgent;
if (/Android (\d+\.\d+)/.test(ua)) {
    var version = parseFloat(RegExp.$1);
    if (version > 2.3) {
        document.write('<meta name="viewport" content="width=640, initial-scale= ' + phoneScale + " ,minimum-scale = " + phoneScale + ", maximum-scale = " + phoneScale + ', target-densitydpi=device-dpi">')
    } else {
        document.write('<meta name="viewport" content="width=640, initial-scale= ' + phoneScale + ' , target-densitydpi=device-dpi">')
    }
} else {
    document.write('<meta name="viewport" content="width=640, user-scalable=no, target-densitydpi=device-dpi">')
};