Js判断客户端是否安装了pdf阅读器

<html>
<head>
<script>
    function isAcrobatPluginInstall() {
        var flag = false;
        // 如果是firefox浏览器    
        if (navigator.plugins && navigator.plugins.length) {
            for (x = 0; x < navigator.plugins.length; x++) {

                if (navigator.plugins[x].name == \'Adobe Acrobat\')
                    flag = true;
            }
        }
        // 下面代码都是处理IE浏览器的情况    
        else if (window.ActiveXObject) {
            for (x = 2; x < 10; x++) {
                try {
                    oAcro = eval_r("new ActiveXObject(\'PDF.PdfCtrl." + x + "\');");
                    if (oAcro) {
                        flag = true;
                    }
                } catch (e) {
                    flag = false;
                }
            }
            try {
                oAcro4 = new ActiveXObject(\'PDF.PdfCtrl.1\');
                if (oAcro4)
                    flag = true;
            } catch (e) {
                flag = false;
            }
            try {
                oAcro7 = new ActiveXObject(\'AcroPDF.PDF.1\');
                if (oAcro7)
                    flag = true;
            } catch (e) {
                flag = false;
            }
        }
        if (flag) {
            alert("yes");
            return true;

        } else {
            alert("对不起,您还没有安装PDF阅读器软件呢,为了方便预览PDF文档,请选择安装！");
            location = \'http://ardownload.adobe.com/pub/adobe/reader/win/9.x/9.3/chs/AdbeRdr930_zh_CN.exe\';
        }
        return flag;
    }  
</script>
</head>
<body>
<input type="button" value="jiance" onclick="isAcrobatPluginInstall()"/>
</body>
</html>