forLoopES5.js

var Arr = [3, 6, 9, 12, 15, 18, 21];
Arr.author="Gurucharan";

//Using legacy for loop
console.log('==============[Legacy for loop]==============');
for (var i = 0; i < Arr.length; ++i) {
  console.log("index is of type", typeof i, Arr[i]);
}

//Using forEach
console.log('==============[for-each loop]==============');
Arr.forEach(function (element, i) { //index i is optional
  console.log("index is of type", typeof i, element);
});

//Using for-in loop
console.log('==============[for-in loop]==============');
for (i in Arr){
  console.log("index is of type", typeof i, Arr[i]);
}