native.js 判断是否安装某app

例：是否安装微信

      function isWeixin() {
        var UIApplication = plus.ios.importClass("UIApplication");
        var NSURL = plus.ios.importClass("NSURL");

        var app = UIApplication.sharedApplication();
        var bdScheme = NSURL.URLWithString("baidumap://");
        var install = app.canOpenURL(bdScheme);

        plus.ios.deleteObject(bdScheme);
        plus.ios.deleteObject(app);
      }

　　检查app是否存在 canOpenURL

　　常用的 https://blog.csdn.net/Maple_ROSI/article/details/79470056