https://github.com/ialcazar/JavaScript-Examples/blob/master/arrays/concatenator/concatenator.js

concatenator.js

var concatenate = (function(){
   var params;
   
   //Auxiliares "privados"

   function hasElements(){return params.length>0;}

   function createString(){
      var res = "";
      for(var i=0;i<params.length;i++){
            res += params[i];
            if(isNotLastParam(i)){res+=",";}
      }  
      return res;
   }

   function isNotLastParam(p1){
      return (p1<params.length-1);
   }

   //La lambda protagonista

   return function(parameters){
      var result = "";
      params = parameters || [ ];
      if(hasElements()){result = createString();}  
      return result;
   }
})();