enumeration - Writing an enumerator for a JavaScript object -

i'm trying understand how enumerator javascript object can written. came across piece of sharepoint code items of sp list being obtained on client side, , code similar 1 below being performed on sharepoint object.

var enumerator = list.getenumerator(); while(enumerator.movenext()) {     var currentitem = enumerator.getcurrent();     // actions on currentitem } 

if write custom object iterated upon using enumerator above, how look? attempt, doesn't work:

var list = {     items: ["a", "b", "c", "d", "e"],     counter: -1,     enumerator: {         movenext: function() {             counter++; // outer object's variable not accessible             if(counter >= items.length)                 return false;             else                 return true;         },         getcurrent: function() {             return items[counter]; // outer object's variable not accessible         }     },     getenumerator: function() {          return this.enumerator();      } }  var enumerator = list.getenumerator(); while(enumerator.movenext()) {     var currentitem = enumerator.getcurrent();     alert(currentitem); } 

can me understand how getenumerator() written function prototype applicable enumerable object?

try below:

var list = function() {     // these local variables accessed inner functions.     var items = ["a", "b", "c", "d", "e"],         counter =  -1;     return {         enumerator: {             movenext: function() {                 counter++;                  return counter < items.length;             },             getcurrent: function() {                 return items[counter];              }         },         getenumerator: function() {              // here should not return this.enumerator() this.enumerator             return this.enumerator;          }     }; };  var enumerator = list().getenumerator(); while(enumerator.movenext()) {     var currentitem = enumerator.getcurrent();     alert(currentitem); } 

the jsfiddle demo.