ProGrad Lab | Arrays & Functions

Introduction

Manipulating arrays is a very common operation we perform while programming. Whether you're calculating the total order value for a shopping cart, grabbing only the first names out of a list, or moving a piece on a chessboard, you're going to be modifying or manipulating an array to get the result.

In a similar fashion, you are gonna perform a few array & function related operations in this lab. Go to the src/functions-and-arrays.js file and complete all the unfinished code to complete this challenge. You can see the output in browser console

What should you do

Fork this repo
Clone this repo
Practice JavaScript - Arrays

How To Submit

Upon completion, run the following commands:

git add .
git commit -m "ProGrad ID"
git push origin master

And finally, create a pull request so your ProGrad Mentor (PM) can review your work.

Tests

Open the SpecRunner.html file on your browser and start coding to pass the test. Remember to focus on one test at a time and read carefully the instructions to understand what should be done.

Progression #1: Greatest of the two

Define a function greatestOfTwoNumbers that takes two numbers as arguments and returns the greatest number.

Progression #2: The lengthy word

Declare a function named findScaryWord that takes as argument an array of names and returns the name which contains the maximum characters. If there are 2 names with the same number of characters, it should return the first occurence with max characters.

You can use the following array to test your solution:

const words = ['George', 'Alice', 'Alex', 'John', 'Infanta', 'Xavior', 'LourdhAntony'];

Progression #3: Net Price

Calculating a sum can be as simple as iterating over an array and adding each of the elements.

John spent his money on buying groceries, he wants to find the net amount that he had spent in the super market.

Declare a function named netPrice that takes an array of prices as an argument, and returns the sum of all items in the array. Later in the course we'll learn how to do this by using the reduce array method, which will make your work significantly easier. For now, let's practice "declarative" way - adding values, using loops.

You can use the following array to test your solution:

const prices = [200, 120, 100, 108, 135, 162, 25, 170, 80, 110];

Progression #3.1 (Bonus): A generic sum() function

The goal: Learn how to refactor your code. :

In progression 3, you created a function that returns the sum of an array of prices. But what if we wanted to know how much is the sum of the length of all of the words in an array? What if we wanted to add boolean values to the mix? We wouldn't be able to use the same function as above, or better saying, we would have to tweak it a little bit so that it can be reused no matter what is in the array that is passed as argument when function sumOfArray() is called.

Here we're applying a concept we call polymorphism, that is, dealing with a functions' input independent of the types of data passed.

Let's create a new function add() that calculates the sum for array filled with (almost) any type of data. Note that strings should have their length added to the total, and boolean values should be coerced into their corresponding numeric values. Check the tests for more details.

You can use the following array to test your solution:

const mixedArr = [63, 122, 'audi', 61, true, 'volvo', '20', 'lamborghini', 38, 156];

// should return: 463

Progresson #4: Mid point

Calculating the mid point is an extremely common operation. Let's practice it a bit.

The logic behind this:

1. Find the sum as we did in the first exercise (or how about reusing that the sumOfArray()?)
2. Take that sum and divide it by the number of elements in the list.

Progression 4.1: Array of numbers

Consider a Surveyor is leveling a road and making notes of it. He wants to find the mid point of all those levels.

Declare a function named midPointOfLevels that expects an array of numbers and returns the average of the numbers:

Starter Code

const levels = [22, 16, 9, 10, 7, 14, 11, 9];

Progression 4.2: Array of strings

Declare a function named averageWordLength that receives as a single argument an array of words and returns the average length of the words:

Starter Code

const items = [
  'bread',
  'jam',
  'milk',
  'egg',
  'flour',
  'oil',
  'rice',
  'coffee powder',
  'sugar',
  'salt'
];

Progression #4.3 (Bonus): A generic avg() function

Create function avg(arr) that receives any mixed array and calculates average. Consider as mixed array an array filled with numbers and/or strings and/or booleans. We're following a similar logic to the one applied on the bonus iteration 4.1 😉

const mixedArr = [63, 122, 'audi', 61, true, 'volvo', '20', 'lamborghini', 38, 156];

// should return: 46.3

Progression #5: Unique arrays

Take the following array, remove the duplicates, and return a new array. Check out the indexOf Array method.

Do this in the form of a function uniqueArray that receives an array of words as a argument.

Starter Code

const items = [
  'bread',
  'jam',
  'milk',
  'egg',
  'flour',
  'oil',
  'rice',
  'coffee powder',
  'sugar',
  'salt',
  'egg',
  'flour'
];

Progression #6: Find elements

Let's create a simple array search.

Declare a function named searchElement that will take in an array of words as one argument, and a word to search for as the other. Return true if it exists, otherwise, return false. Don't use indexOf for this one.

Starter Code

const words = [
  'door',
  'window',
  'ceiling',
  'roof',
  'plinth',
  'tiles',
  'ceiling',
  'flooring'
];

Progression #7: Count repeated elements

Declare a function named howManyTimesElementRepeated that will take in an array of words as the first argument, and a word to search for as the second argument. The function will return the number of times that word appears in the array.

Starter Code

const words = [
  'machine',
  'matter',
  'subset',
  'trouble',
  'starting',
  'matter',
  'eating',
  'matter',
  'truth',
  'disobedience',
  'matter'
];

Progression #8 (Bonus): Product of adjacent numbers

What is the greatest product of four adjacent numbers? Any four numbers that are next to each other horizontally or vertically are considered adjacent.

For example, if we have a 5x5 Matrix like:

[ 1,  2, 3, 4, 5]
[ 1, 25, 3, 4, 5]
[ 1, 20, 3, 4, 5]
[ 1, 20, 3, 4, 5]
[ 1,  4, 3, 4, 5]

The greatest product will be the 25x20x20x4 = 40000;

Declare a function named maximumProduct(matrix) to find it in the 10x10 grid below!

const matrix = [
  [08, 02, 22, 97, 38, 15, 00, 40, 00, 75],
  [49, 49, 99, 40, 17, 81, 18, 57, 60, 87],
  [81, 49, 31, 73, 55, 79, 14, 29, 93, 71],
  [52, 70, 95, 23, 04, 60, 11, 42, 69, 24],
  [22, 31, 16, 71, 51, 67, 63, 89, 41, 92],
  [24, 47, 32, 60, 99, 03, 45, 02, 44, 75],
  [32, 98, 81, 28, 64, 23, 67, 10, 26, 38],
  [67, 26, 20, 68, 02, 62, 12, 20, 95, 63],
  [24, 55, 58, 05, 66, 73, 99, 26, 97, 17],
  [21, 36, 23, 09, 75, 00, 76, 44, 20, 45]
];

Progression #8.1 (Bonus): Product of diagonals

Following the logic you've used in iteration #8, declare a function called maximumProductOfDiagonals(matrix). It takes a matrix as a parameter and returns the greatest product of any four values layed out diagonally, in either direction.

Happy Coding ProGrad ❤️