[MUSIC]

Hey there.

Ashley here.

Today we're going to be Practicing Working With Const and

Let Variables in JavaScript.

This is a follow up to the first part of the Getting Started With ES 2015 Course.

Defining variables with let and const.

If you haven't finished that section yet or are unfamiliar with const and

let variables, now might be a good time to go and review those videos.

I've included a link to them in the teacher's notes.

In this practice session,

you'll be writing a function, editing a function, and

changing some other code to help you get a feel for how const and let variables work.

And how they're different from variables declared with a var keyword?

There's a workspace attached to this video that includes the file you'll

be working out of with some more detailed instructions.

You'll use the workspace console and node to run your code.

Node, if you haven't used that before is a way to run JavaScript code

outside of your browser.

This workspace is all set up to use node.

So when you're ready to run your file, open up the work space console,

type node followed by a space and then the name of your file.

In this case, let_const.js then hit Enter.

There's a note on how to do this in the instructions as well.

Go ahead and open up the let_const.js file.

Inside you'll see here instructions written as JavaScript comments

at the top of the file.

After these instructions, you'll see three variable declarations.

The first is teachers, an array containing one object.

Object should be familiar to you from the JavaScript Loops, Arrays and

Objects course.

The second variable declaration is courses.

An array containing six JavaScript course titles.

Finally, we've declared i.

A variable that's equal to the length of the courses array.

After these variable declarations, you'll see a function called add new teachers.

That takes one parameter, newTeachers.

But whoops, something's missing here.

Our addNewTeachers function doesn't have any code inside of it.

Your first goal is to complete this function by writing some code that lets us

add new teachers to our teachers array.

After the addNewTeachers function,

you'll see a function called printTreehouseSummary.

This function runs but it's outputting an incorrect number of treehouse, teachers,

and courses.

Use what you know about let and const in JavaScript to fix this function so

it logs the correct numbers to the console.

Now don't worry if the string format used in the console.logs are unfamiliar to you.

I'm using something called template literals which offer a more concise and

simple way to display string data in ES2015.

You'll learn all about template literals in the next segment of

the Getting Started With ES2015 Course.

If you are to run your code at this point, you would get an error message.

Your final goal for

this practice session is to figure out what's causing the error and fix it.

The error message in the consul should give you some clues about where to start

and if you're really stuck check the teacher's notes for a hint.

Once you've completed this three tasks you should be able to run your code.

Now remember to run your code you're gonna type node, then the name of the file,

which is let_const.js and then hit Enter.

Now if your code works correctly, your output should look just like this.

If you think you're ready to get started go ahead and try to program your solution.

If you're having trouble, that's 100% okay.

Practicing, trying new things, and playing around with code,

is part of how we learn, and is a vital part of programming.

Either way, come back and watch video two to check your work and see my solution.

If you're looking for some more background info,

don't forget to check the teacher's notes for links to related coursework.

See you soon.