Javascript Map Calling directly or Generically

js_map_generic

function genericallyCallingMap(dna) {
  var complements = {"C":"G", "G":"C", "T":"A", "A":"U"};  
  var map = Array.prototype.map
  var a = map.call(dna, function(x) {
     return complements[x];
   })
  return a.join("");
};
function callingMapOnAnArray(dna) {
  var a = dna.split("").map( function(x) {
      return complements[x]; 
    });
  return a.join("");
};