title: How to get the before upload event at the elfinder plugin (a file manager plugin)
body: <p>I am working on the file manager using jquery</p>
  
  <p>here is the code:</p>
  
  <pre><code> var elfinder = $('#elfinder').elfinder({
              url: '&lt;?= $connector; ?&gt;',
              soundPath: '&lt;?= site_url('assets/plugins/elFinder/sounds/rm.wav'); ?&gt;',
              height: 700,
              lang: 'zh_TW',
              uiOptions: {
                  // toolbar configuration
                  toolbar: [
                      ['back', 'forward'],
                      ['reload'],
                      ['mkdir', 'upload'],
                      ['copy', 'cut', 'paste', 'rm'],
                      ['rename'],
                      ['view', 'sort']
                  ]
              },
              contextmenu: {
                  navbar: ['open', '|', 'copy', 'cut', 'paste', 'duplicate', '|', 'rm', '|', 'info'],
                  cwd: ['reload', 'back', '|', 'upload', 'mkdir', 'paste', '|', 'info'],
                  files: [
                      'open', 'quicklook', 'sharefolder', '|', 'download', '|', 'copy', 'cut', 'paste', 'rm', '|', 'rename', '|', 'info'
                  ]
              },
              ui: ['toolbar', 'tree', 'stat'],
              handlers: {
                  add: function (e) {
                  },
                  upload: function (e, instance) {
                      alert("test1");
                      //alert("test2");
                      //return false;
                      //console.log(event.data);
                      //console.log(event.data.selected); // selected files hashes list
                  }
              }
          });
  </code></pre>
  
  <p>The problem are,</p>
  
  <p>1) I would like to have some checking before file upload, if fail then cancel the upload, but in either add / upload event it is fire after upload start , and fire several time</p>
  
  <p>2) Also, it can't capture the on upload complete event as the upload event fire several time </p>
  
  <p>Here is the event list:</p>
  
  <p><a href="https://github.com/Studio-42/elFinder/wiki/Client-event-API">https://github.com/Studio-42/elFinder/wiki/Client-event-API</a></p>
  
  <p>Any suggestion , thanks a lot for helping.</p>
  
  <p>Updated:</p>
  
  <p>Find in Server side, there is a bind options , to override the command e.g. "rm mkdir" etc... however , I would like to get the user id when store, so are there list of event that I can override in client side? Thanks</p>
  
  <p><a href="https://github.com/Studio-42/elFinder/wiki/Connector-configuration-options">https://github.com/Studio-42/elFinder/wiki/Connector-configuration-options</a></p>