How to Install App from sharepoint hosted app to sub sites+javascript

Question

I need to install my sharepoint app from root site to other sub sites programmatically using javascript. but my installation function doesn't work:

 function InstallApp()
  { 
    var context = new SP.ClientContext(appweburl);
var factory = new SP.ProxyWebRequestExecutorFactory(appweburl);
context.set_webRequestExecutorFactory(factory);

var installContext = new SP.AppContextSite(context, hostweburl + '/subSite');

var installWeb = installContext.get_web();

var appFile = installWeb.getFileByServerRelativeUrl('/SiteAssets/myAppFile.app');

installWeb.loadAndInstallApp(appFile);
installWeb.update();

installContext.get_context().load(installWeb);
installContext.get_context().executeQueryAsync(onInstallSuccess, OnFailure); 
  }