Batch delete based on condition

Is it possible to delete `records` in *batch* using NodeJS based on *condition*?
Below is sample code for batch delete, but preparing `taskKey1`, `taskKey2`... etc is not a elegant as putting condition like `size > 25`

```js
const keys = [taskKey1, taskKey2];

datastore.delete(keys)
  .then(() => {
    // Tasks deleted successfully.
  });
```