Iterate Over Arrays Using JavaScript - ES5 Vs ES6

There are several ways for iterating over arrays. The traditional way is using for and while loop, we can use forEach loop and ES6 has introduced for-of loop also.

Using ES5

Observe below code, we are following traditional approach here

var arr = ['a', 'b', 'c'];
for (var i=0; i<arr.length; i++) {
  var elem = arr[i];
  console.log(elem);
}

Variable i is available in global scope. Use let keyword instead of var to avoid polluting global scope

Click here to see DEMO

ES5 provides forEach loop also. Observe below code. It will pass value to different function

var arr = ['a', 'b', 'c'];
arr.forEach(function (elem) {
    console.log(elem);
});

Click here to see DEMO

ES5 provides for-in loop also. You can work with indexes

var arr = ['a', 'b', 'c'];
for (var i in arr) {
   console.log(i+'  '+arr[i]);
}

Click here to see DEMO

Using ES6

Observe below for-of loop. Constant elem holds element in array.

const arr = ['a', 'b', 'c'];
for (const elem of arr) {
   console.log(elem);
}

Click here to see DEMO
If you want to work with indexes too, then use new Array method entries()

const arr = ['a', 'b', 'c'];
for (const [index, elem] of arr.entries()) {
    console.log(index+'. '+elem);
}

Click here to see DEMO

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