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Web applications typically update data from servers (eg. whether, time, streaming media, dollar rates, thread posts). Developers have to overcome the issue of using obsolete data due to a late response of a server. For example, consider a website that shows an streaming media using several ajax requests. If responses of ajax requests are retrieved in wrong order, the streaming media cannot be observed correctly. A solution could be to wait for all frames, however, this solution could delay to much the streaming media. A better solution is to discard the late frames to show the animation. The DiscardLate strategy discards the late responses of ajax requests (obsolete responses). As an example, we present below a streaming media about the rotation of the Earth (the streaming media is finite by simplicity). This example shows the effects that reproduce in a streaming media when frames in a random order.

When the “activate order” button is clicked, the streaming media is always showed a correct flow (right to left). When the “deactivate order” button is clicked, the streaming media is showed a random flow. NOTE: You have to wait until a new streaming media to see the effect over.

The implementation follows: Toggle between the code and example

The DiscardLate strategy is implemented as a TM advice, which is a JavaScript function, that is executed every time a response of ajax request is retrieved:

var discardLate = function(jp) {
  if(!this.isLate(jp)){     //is obsolete this join point?
    jp.proceed();
    this.updateCr(jp); //notifies that join point was executed.
  }
}

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