Demonstration of reducing a messy, verbose `for loop` using functional approach for terse, concise solution.

verboseForLoop.js

/**
 * Traditional solution: For-loop usage
 */
function buildEpisodes(markers) 
{
  var result = [],i, newEpisode;
  
  if (markers && markers.length > 0) {
    for (i = 0; i < markers.length; i++) {
      newEpisode = makeEpisode(markers[i]);
      if (newEpisode) {
          result.push(newEpisode);
      }
    }
  }

  return result;
};

/**
 * Functional Solution: Same logic, but concise and terse !!
 * NOTE: includes morphic wrapping of `markers`
 */
function buildEpisodes_v2( markers ) 
{
  var isNotNull = function( it ){ return it != null; };
  return [ ].concat( markers ).map( makeEpisodes ).filter( isNotNull );
}

@sesteva,
You are correct that [under normal conditions] I do not need the [ ].concat().

Now consider what happens if ( markers == null ) or markers is not an instance of Array?
Using [ ].concat() insures that it will always be an Array instance before the .map() invocation.