asyncExample.js

function processOneVideo(video, cb) {
  if(doesVariableHaveNoValue(video.videotitle)){
      video.videotitle="Product video";
  }
  /* -----+++++-----+++++----- ZALGO TERRITORY -----+++++-----+++++----- */
  if(doesVariableHaveNoValue(video.videothumb)){
      video.videothumb= urlCorrector.convertUrl(video.videourl,function(err,res){
          video.videourl=res;
          cb(err);
      });
  }
  else{
       urlCorrector.convertUrl(video.videothumb, function (err, res) {
           video.videothumb=res;
           cb(err);
       });
  }
}

function processAllVideos(videoList, cb) {
  async.map(videoList, processOneVideo, cb);
}

module.exports = processAllVideos;

if (require.main === module) {
  
  processAllVideos([
      { videourl: "http://vimeo.com/blalba" },
      { videourl: "http://youtube.com/blabla" }
    ], function () { 
      console.log(arguments); 
      // arba
      if (video[0].videothumb != "blabla") {
        console.error("unexpected thumb returned")
      }
    })

}