Simple Functions Lab

This lab aims to give you more practice writing functions and solving problems.

Instructions

As you're writing your functions, it's important to code a little and test a little. It's easier to fix a few bugs at a time than to have to fix a ton of bugs at the end. There are three ways in which you can test your code.

* Using the browser
* Using `node`
* Using the automatic test cases your instructors have provided

Question 1 Walkthrough

Code along as we show you how to solve Question 1. Write a function that takes a name and returns a greeting with "Hello" and the person's name.

Example:

hello("Carmen"); // "Hello, Carmen!"

In your code in the answers.js file, write:

function hello(name) {
  return `Hello, ${name}!`;
}

Testing using the Browser

To test your code using the browser, open your index.html in a new tab. Because your HTML has a <script> tag to your JavaScript file, they are linked together. Open the console in your HTML webpage and invoke the function to verify it has the expected output. You can ignore the error about module is not defined and the error about Failed to load resource.

Testing using node

You can run JavaScript outside the browser using the command node <path_to_file>. From your terminal, you must be in the project folder where answers.js is located. Then you can run the file from the terminal with node answers.js.

However, this will not print anything out yet!

We declared our function but we never invoked it! We can invoke functions in the browser's console, but we can't invoke functions in the terminal. Instead, we must invoke the function in the file itself, then run the file. Update your code in answers.js to invoke the function:

hello("Carmen"); // Remember hoisting is a thing ;)

// Question 1
function hello(name) {
  return `Hello, ${name}!`;
}

Save your file. If we run nodes answer.js, we get... still nothing...

Although we have invoked the function, we never tell our program to do anything with the function's return value. Let's make a change to print out the return value of our function:

console.log( hello("Carmen") ); // Logs "Hello, Carmen!"

// Question 1
function hello(name) {
  return `Hello, ${name}!`;
}

Save your file. Now run node answers.js in the terminal to see the expected output.

Testing using Automated Test Cases

Your instructors have written some test cases in the file answers.text.js. DO NOT change anything in this file. These tests cases are very similar to the test cases you might have seen on CodeWars.

From the terminal run npm install to install dependencies. You only have to run this command once per lab/assignment.

Then run npm test to see the results.

Coding Exercises

1. Write a function that takes a name and returns a greeting with "Hello" and the person's name.

   Example:

   hello("Carmen"); // "Hello, Carmen!"
   hello("Devonte"); // "Hello, Devonte!"
   hello("Reuben Ogbonna"); // "Hello, Reuben Ogbonna!"

2. Write a function that takes in two numbers and returns the product (multiply those numbers together):

   Examples:

   findProduct(5, 7); // 35
   findProduct(15, 10); // 150
   findProduct(25.75, 42); // 1081.5

3. Write a function that returns the area of a square when given one side as the input:

   Examples:

   getSquare(5); // 25
   getSquare(4); // 16
   getSquare(3); // 9

4. Write a function that takes in a number and returns the opposite of that number. If the original number is positive, return the negative version of that number. If the original number is negative, return the positive veresion of that number.

   Examples:

   makeOpposite(9); // -9
   makeOpposite(-3); // 3
   makeOpposite(5.78); // -5.78

5. Write a function that logs all even numbers from 0 to 50, inclusive, to the console. Log all numbers on separate lines. Then, this function should return the string, "Why is 6 afraid of 7?".

   Example:

   logEvenNumbers(); // "Why is 6 afraid of 7?"
   
   /* Printed to the Console */
   // 0
   // 2
   // 4
   .
   .
   .
   // 48
   // 50

6. Write a function that returns the sum of all numbers between 1 and some other number, inclusive, that are multiples of 4 or 7. For example, if the supplied number is 17, the result should be 61 (4 + 7 + 8 + 12 + 14 + 16).

   You may assume that the number passed in is an integer greater than 1.

   Examples:

   sumFoursAndSevens(17); //(4 + 7 + 8 + 12 + 14 + 16) => 61
   sumFoursAndSevens(21); //(4 + 7 + 8 + 12 + 14 + 16 + 20 + 21) => 102

7. Write a function that takes one argument, a positive integer, and returns a string of alternating 'X's and 'O's, always starting with a 'X'. The length of the string should match the given integer.

   Examples:

   exsAndOhs(6);    // "XOXOXO"
   exsAndOhs(9);    // "XOXOXOXOX"
   exsAndOhs(4);    // "XOXO"
   exsAndOhs(7);    // "XOXOXOX"

Challenge functions:

There are no automated test cases for the following problems. You will be responsible for testing them yourselves manually, either using the browser or node.

1. Write a function weirdString() that takes in a string and returns a copy of that string with every vowel removed, and then of the remaining letters, every other letter alternates between lowercase and uppercase.

weirdString("hello world") // "hLl wRlD"
weirdString("Reuben Ogbonna") // "rBn gBnN"
weirdStsring("Maya Bhattacharjee-Marcantonio") // "mY BhTtChRj-mRcNtNi"

2. Write a function possibleSums() that takes in an integer. It returns an array of all possible sums of every two digits combination within that number.

For example, given the number 12345, all possible sums of every two digit combination from that number are:

[ 1 + 2, 1 + 3, 1 + 4, 1 + 5, 2 + 3, 2 + 4, 2 + 5, 3 + 4, 3 + 5, 4 + 5 ]

So the function should return [ 3, 4, 5, 6, 5, 6, 7, 7, 8, 9 ].