HTML5 Javascript从Async函数返回值

Question

如何让返回客户从此功能实际返回客户数组？我的意思是另一种语言，我会使用Thread.SignalOne或Async callback。我怎么能在JS中这样做？

 var getAllFiles = function() {
 var customers = [];
 var objectStore = dbGlobals.db.transaction("files").objectStore("files");

 objectStore.openCursor().onsuccess = function(event) {
  var cursor = event.target.result;
  if (cursor) {
      if(cursor.key.indexOf(currentFolder) != -1)  {
        customers.push(cursor.value);
      }
      cursor.continue();      
  }
  else {
//  alert("Got all customers: " + customers);
    return customers;
  }
};

}