title: How to Install App from sharepoint hosted app to sub sites+javascript
body: <p>I need to install my sharepoint app from root site to other sub sites programmatically using javascript. but my installation function doesn't work:</p>
  
  <pre><code> 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); 
    }
  </code></pre>