buffalocheck/functions-lab

Functions Lab (90 mins)

STUDENT PRE-WORK

Before this lesson, you should already be able to:

• Differentiate between data types (strings, numbers, Booleans).
• Use if/else if/else conditionals to control program flow based on Boolean conditions.
• Create and manipulate arrays.
• Use loops to iterate through the elements in an array.
• Describe why functions are useful.
• Describe how parameters relate to functions.
• Explain how return statements are used in JavaScript.

Introduction

Note: This can be a pair programming activity or done independently.

Let's practice writing some functions!

Exercise

Requirements

Follow the requirements in the list below:

1. Define a function maxOfTwoNumbers that takes two numbers as arguments and returns the largest of them. Use the if-then-else construct available in JavaScript. Do some Googling to figure this out if you forget how conditionals work.
2. Define a function maxOfThree that takes three numbers as arguments and returns the largest of them.
3. Write a function isCharacterAVowel that takes a character (i.e., a string of length 1) and returns true if it is a vowel and false otherwise.
4. Define a function sumArray and a function multiplyArray that sums and multiplies (respectively) all the numbers in an array of numbers. For example, sumArray([1,2,3,4]) should return 10, and multiplyArray([1,2,3,4]) should return 24.
5. Write a function that returns the number of arguments passed to the function when called.
6. Define a function reverseString that reverses a string. For example, reverseString("jag testar") should return the string "ratset gaj".
7. Write a function findLongestWord that takes an array of words and returns the length of the longest word in the array.
8. Write a function filterLongWords that takes an array of words and a number i and returns a new array of words that are longer than i characters long.

Bonus For this bonus, you'll have to do some research on objects.

1. Write a function that takes a string as an argument and returns an object where:

• The keys are the characters that occur in the string.
• The values are the number of occurrences for each letter, regardless of the case.

For example, calling the function with the string "General Assembly" will return:

{
  a: 2,
  b: 1,
  e: 3,
  g: 1,
  l: 2,
  m: 1,
  n: 1,
  r: 1,
  s: 2,
  y: 1
}

Starter Code

Open the file main.js. All the function names are already inside the file; you just need to implement the functions by adding code inside each one.

Use the Chrome Dev Tools console to practice executing your code.

Alternately, you can add console.log(); statements in your main.js file; then you should see the values displayed in the console when you open the index.html file in your browser.

Deliverable

You'll review the answers with the instructor in class.

ADDITIONAL RESOURCES

• Readings
  • MDN Functions