callbackDemo_02.js

function CrawlingAWebPageAndGetLinks(callback){
  // do the stuff the method pretend;
  var value = Crawler.Get("https://www.google.com/search?q=callback%20hell");
  // then use
  callback(value);
}

(function program(){
  var callback = function(v){
    console.log(v);
  };
  var result = CrawlingAWebPageAndGetLinks(callback);
})();