title	type	competencies	creator
JS Functions	homework	JS basics	cohort adapted by WDIR-Matey Christine Yi for WDIR

Fun Fun Functions!

Javascript functions are essential in developing functionality (who knew?) in our programs, but sometimes there's some funky behavior, and it doesn't do what we might expect it to do, especially when it comes to variable scope. In tonight's assignment, you will start by exploring local and global scope in Javascript and see how being able to access variables depends on the scope. You'll round off your knowledge by writing some functions and use Mocha tests to check your work.

The general guideline with variable scope is:

• Any variable declared outside a function belongs to the global scope.
• Global variables are accessible anywhere in your code.
• Each function has its own scope.
• Variables declared in those functions are local, meaning it's accessible only inside that function and any nested functions.
• The newest version of Javascript (ES6) offers block scoping which we won't be using here.

Exercise Objectives

• Gain deeper insight to local and global scope.
• Practice writing functions that take 1 - 2 arguments.
• Use tests to test your work.

Setup

cd into today's homework directory, and run npm install in terminal -- this will download any assignment-specific JavaScript dependencies into to a directory called node_modules.

Tests Setup

There are automated tests built into this assignment so that you can check your work. You can run these tests by running npm test in terminal in the homework directory. Ideally, you should run the tests after each problem. Only the Questions 6 - 10 have tests provided for you.

Instructions

• Write your answers in script.js.
• For Questions 1 - 5:
  • fill in the blank with either local or global or out of scope.
  • These are (super) short answer questions.
  • Feel free to run the code in script.js or in a repl.it session, or in your browser console.
• For Questions 6 - 10:
  • don't modify the variable names, since the tests use them.
  • run npm test in a separate terminal tab after each problem and get them all to pass.

Question 1

1. The variable greeting is ______ to the sayGreeting function.
2. Can the function access greeting?
3. What happens when you invoke sayGreeting?
4. 🎯 Commit -m "Question 1 done"

var sayGreeting = function() {
	var greeting = "Aloha!";
  console.log(greeting);
}

Question 2

1. The variable number is _______ to the addition function.
2. Can the function access number?
3. What happens when you invoke addition?
4. 🎯 Commit -m "Question 2 done"

var number = 5;

var addition = function() {
	console.log(number)
}

Question 3

1. The variable vegetable is _______ to the firstFunction function.
2. The variable vegetable is _______ to the second Function function.
3. Can the secondFunction access vegetable?
4. What happens when you invoke firstFunction?
5. What happens when you invoke secondFunction?
6. 🎯 Commit -m "Question 3 done"

var firstFunction = function() {
	var vegetable = "snap pea";
	console.log(vegetable);
}

var secondFunction = function() {
	console.log(vegetable);
}

Question 4

1. The variable superhero is _______ to the fightSuperman function.
2. The variable superhero is _______ to the theRealHero function.
3. What happens when you invoke fightSuperman?
4. What happens when you invoke theRealHero?
5. Does theRealHero have access to superhero inside fightSuperman?
6. 🎯 Commit -m "Question 4 done"

var superhero = "Batman";

var fightSuperman = function() {
	var superhero = "Superman";
	console.log(superhero);
}

var theRealHero = function() {
	console.log(superhero);
}

Question 5

1. The variable beep is in _______ scope.
2. What happens when you execute the code below?
3. Is makeNoise a function declaration or function expression?
4. Change the syntax for makeNoise so that it's a function expression. What happens when you execute the code?
5. What happens if you move makeNoise() after the function expression?
6. What happens if you console.log(beep) below this revised code?
7. Go back to the original code. What happens if you throw a console.log(beep) after the function? How is this possible? (This is why we'll be mostly sticking to function expressions.)
8. 🎯 Commit -m "Question 5 done"

makeNoise();

function makeNoise(){
  beep = "beep";
  console.log(beep);
}

Question 6

Build upon the sumOfNums function so that:

• it takes an array of numbers
• it outputs the sum of numbers that were passed in
• Edge case: if the array is empty, it returns 0
• 🎯 Commit -m "Question 6 test passed"

Question 7

Build upon the numsGreaterThanTen function so that:

• it takes an array of numbers
• it outputs an array of the numbers from the first array that are strictly greater (i.e. greater than but not equal to) than 10
• 🎯 Commit -m "Question 7 test passed"

Question 8

Build upon the allStartingWithA function so that:

• it takes an array of words
• it outputs true if ALL words start with the letter 'a' (case-insensitive), and false otherwise.
• Edge Case: If the array is empty, the function should return true.
• 🎯 Commit -m "Question 8 test passed"

Question 9

Build upon the hasAtLeastNVowels function so that:

• it takes 2 parameters: a single word, and a number (n)
• it outputs true if the word has at least some number (n) of vowels, false otherwise
• Assume that vowels are 'a', 'e', 'i', 'o', and 'u' (NOT 'y')
• Edge Case: If n is less than zero, return null.
• 🎯 Commit -m "Question 9 test passed"

Question 10

Build upon the buildObjectFromWords function so that:

• it takes an array of words
• it outputs an object {} where each word in the array is a key, and the value tied to that key is the length of the word
• e.g. given ['cat', 'horse', 'elephant'], return { cat: 3, horse: 5, elephant: 8}
• 🎯 Commit -m "Question 10 test passed"

Reach Goal

We'll be writing a ton more functions during the course, and it never hurts to practice more and feel super cozy about functions. One really great resource we'll be using in class is Code Wars, a great training grounds for coding challenges for basically every programming language!

1. Sign up on Code Wars
2. For "Programming experience", select Learning to Program
3. For "Choose a language", select JavaScript

Try your hand at one (or all) of these challenges:

1. Bronze status
2. Silver status
3. Gold status
4. Plat challenge

Submitting Your Work

When you're ready, create an issue on the class repo with a title in the format "First and Last Name -- Week XX Day XX". The issue body should have:

• A link to your forked repo (ie. to your homework folder)
• A 'comfort' score on how you feel about your answers, from 1 (very uncomfortable) to 5 (very comfortable)
• A 'completeness' score, from 1 (didn't do it) to 5 (finished all of it)
• A 'win'
• A 'struggle'
• A 'comment'
• A screen shot of your tests.