learn-co-students / kwk-l2-js-intro-to-functions-lab-sgharms-test-webdev-fund

Control Flow Lab

Overview

In this lab, we will practice working with functions in JavaScript.

Objectives

1. Practice writing function myFunctionName() { } statements.

2. Practice returning values from within functions.

3. Practice writing functions that accept arguments

Introduction

You have been hired to assist Ed Sheeran's tour management team in the US, and tasked with writing some helpful tools for the team in JavaScript. There are a few reoccurring challenges the team has been having lately that they need help with.

The key word here is reoccurring. In JavaScript, when we have to do the same thing two or more times, it is way more efficient if we write that code once instead of writing the same code over and over. We can then place our code inside a function, calling that function as many times as we need.

In this lab, we're going to practice and explore how functions make our jobs as coders way easier and less repetitive.

Converting to UK Time

For our first task, we need to convert the current local time to UK time (the team has accidentally called a few times after he has gone to bed). So, if we're on the east coast, and it's 4:30pm, it's actually 9:30pm in the UK, 5 hours ahead. On the west coast, 4:30pm is actually 12:30am, 8 hours ahead and Ed is definitely asleep.

JavaScript has some handy built in functions for getting the time, so at any time, we can run the following line to get the current hour wherever we currently are:

new Date().getHours()

This returns the current hour based on the 24 hour clock, so 13 is 1pm, 16 is 4pm, etc... if the number is greater than 12, subtract 12 to get the current hour. So, if we were writing from the east coast and needed to convert to UK time, we would write:

new Date().getHours() + 5 //returns whatever hour it is plus 5

and for the west coast

new Date().getHours() + 8 //returns whatever hour it is plus 8

Writing this isn't too bad, but it is easy to forget the specific parts, and wouldn't it be better if we had a shorter alternative, anyway? Well, we could write a function with an easy to remember name, like getUKTime that always returned the hour in UK time:

function getUKTime() {
  new Date().getHours() + 5
}

getUKTime()
// => UK time compared to Eastern Standard Time

With this function written, every time the management team needs to call Ed, they don't need to remember the specific syntax of writing new Date().getHours(). Depending on the time of day, the results of getUKTime() will be different, but the code is always the same!

Challenge 1

Write the function getUKTime() as you see it above, but feel free to change the amount of hours added to get accurate time (if you're not on the east coast).

Run learn to see how you did!

Discount Tickets

Ed Sheeran is a nice guy. He sometimes gives 20% off discount tickets to his shows. Depending on the original price of the ticket, the tour management team needs a quick way to calculate this discount, regardless of what the original price is.

This is a great use case for adding arguments into a function. An argument is an input, something we pass in when we call the function that is used inside the function. Arguments act similar to variables within a function; we can name them whatever we want, and call that name inside the function knowing that it represents whatever will get passed in when the function is called.

If we had a 100 dollar ticket, for instance, 100 would be the argument being passed in, and we would want our function to take off 20%, in this case, returning 80. If that original price changed to 56 dollars, the discounted price would change to 44.8. We pass arguments in by adding them inside the parentheses at the end of the function name, like so:

function myFunctionWithArguments(myArgument) {
  //do some stuff with myArgument
  //return a dynamic result - the return value is typically dependent on the passed in argument
}

So a real example might be:

function doubleTheInput(input) {
  return input * 2;
}

doubleTheInput(5)
// => 10
doubleTheInput(1)
// => 2
doubleTheInput(-40)
// => -80
doubleTheInput(500)
// => 1000

Challenge 2

Write a function called discountTicket that takes in the original ticket price as an argument and returns a price with 20% off.

Challenge 3: Tweets to Fans

Ed Sheeran has a lot of fans out there, and they love tweeting at him. There are so many tweets that he can't reply to all of them, so he has asked you to write a simple function that, given a fan's twitter account name, returns a string thanking the fan for their support.

Write a function called tweetReply that takes in a string argument (the fan's name) and adds the name in to a short thank you statement: "Hey (insert fan here), thanks so much for the support! I really appreciate it!"

Good luck! Ed Sheeran appreciates your hard work!