When developing an application we inevitably need to iterate over a dataset.

For example, an Ajax request sends back a list of names or an array of objects.

And our program needs to go over each item in the array.

The array for each method provided in ES5 made looping over an array a breeze.

ES2015 gives us a similar but

slightly different technique the, the for of statements.

You can follow along by launching the workspace for this video.

So from the beginning of JavaScripts existence, we've relied heavily

on a basic for loop, where we determine the length of an array and

iterate by increment a variable by one for each pass.

For example let's take a look at the file for-loop.js containing a basic for loop.

If I run the file, the console logs the numbers one through six.

This works well enough but it's cumbersome.

Now ES5 gave us for each to process each item of an array in a callback function.

So if you wanted to control the loop to end it early,

we still had to use the for loop.

Now let's take a look at the file for-each.js which contains

a collection of teachers.

So say I wanted to log only Nick's rating to the console.

Well using for-each it would look something like this.

And when I run this code, I see Nick's rating in the console.

But what I don't see is how many times this function was called so

I'll add another log message outside of my if statement.

We'll say console.log teacher.name.

And you've probably already guessed that the names of online teachers will log

to the console.

So let's see.

And sure enough all nine teacher names are logged.

Luckily, ES2015 has a way to iterate over an array of values and

break out of the loop when needed.

So I'm going to rewrite the for

each loop using the new for of syntax by

typing for let teacher of teachers.

And now I can short circuit the loop or

break out of the loop after it logs Nick by using the break keyword.

So let's give it a try.

Over and the console, I'll run the code.

And now only seven teachers are logged

followed by Nicks rating which is exactly what I expected.

Keep in mind that for of can not be used with regular objects.

You'd want to use the for

in statement instead when looping over object properties.

So check the teachers notes to learn more about four in.

However, for of can be used with any interval object like strings,

arrays, maps, and sets.

Coming up in the next video we'll take a look at set,

a new type of iterable that lets you store unique values.