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JS | Functions & Arrays

Learning Goals

In this exercise you will apply:

  • Array iteration techniques
  • Using functions to manipulate and transform arrays

Introduction

Manipulating arrays in code is a very common operation. Whether you're creating a total for a shopping cart, grabbing only the first names out of a list of people, or moving a piece on a chessboard, you're probably going to be modifying or manipulating an array in some way.

Requirements

  • Fork this repo
  • Clone this repo into your ~/code/labs
  • Write your code in the js file provided in the starter-code

Submission

Upon completion, run the following commands

$ git add .
$ git commit -m 'done'
$ git push origin master

Navigate to your repo and create a Pull Request -from your master branch to the original repository master branch.

In the Pull request name, add your name and last names separated by a dash '-'

Testing Introduction

What is testing?

Software testing is a process of executing an application to validate and verify that it meets the business and technical requirements and works as expected.

Testing is a process, not a single activity. So the process of designing tests early at the beginning of the development and the product's lifecycle can help to prevent deficiencies in the code or product design.

We have created all the tests you need to create the solution, and you have to execute them all and create the code to accomplish all the requirements.

Tests prove that your code actually works in every situation in which it’s designed to work. Even when you are improving the design or creating new features, you can change your current code without breaking what already works.

Testing with Jasmine

Jasmine Logo

Jasmine is an automated testing framework for JavaScript. It is designed to be used in BDD (behavior-driven development) programming which focuses more on the business value than on the technical details.

We have already included Jasmine in the project you just forked, so let's see how to use it to implement our code.

Usage

Before start coding, we will explain the project structure we have provided you:

starter-code/
├── jasmine
│   ├── jasmine-2.8.0/
│   |   └── ...
├── src
│   └── functions-and-arrays.js
├── tests
│   └── FunctionsAndArraysSpec.js
└─ SpecRunner.html

We will be working with the functions-and-arrays.js file inside the src folder. In the jasmine folder you can find all the files that compose Jasmine, that is already linked with the SpecRunner.html file.

Run tests

Run the tests with Jasmine is super easy, you just have to open the SpecRunner.html file in your browser. You will find something like this:

image

Pass the tests

You have to write your code on the src/functions-and-arrays.js file. Following the instructions, you should go step by step passing all the tests.

Do not rush to go through all of them at once, take your time to read carefully about what the iteration is asking you, and solve the errors one by one.

When coding with tests, is super important to read and understand the errors we are having for each test, this way we will know what it expect from your code.

Deliverables

All our work will be located in the functions-and-arrays.js file, so that will be enough. Anyway, you have to push the whole repo to Github.

Find the maximum

Define a function maxOfTwoNumbers that takes two numbers as arguments and returns the largest.

Finding Longest Word

Write a function findLongestWord that takes an array of words and returns the longest one. If there are 2 with the same length, it should return the first occurrence.

Starter Code

var words = [
  'mystery',
  'brother',
  'aviator',
  'crocodile',
  'pearl',
  'orchard',
  'crackpot'
];

Calculating a Sum

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

Semantically reduce is the best method to use for this, but you can use any loop we've discussed so far.

Create a sumArray function that takes an array of numbers as a parameter, and calculate the sum of all its numbers:

Starter Code

var numbers = [6, 12, 1, 18, 13, 16, 2, 1, 8, 10];

Calculate the Average

Calculating an average is an extremely common task. Let's practice it a bit.

Algorithm

  1. Find the sum as we did in the first exercise
  2. Take the sum from step 1, and divide it by the number of elements in the list.

Level 1: Array of Numbers

Write a function averageNumbers that receives an array of numbers and calculate the average of the numbers:

Starter Code

var numbers = [2, 6, 9, 10, 7, 4, 1, 9];

Level 2: Array of Strings

Write a function averageWordLength that receives an array of words and calculate the average length of the words:

Starter Code

var words = [
    'seat',
    'correspond',
    'linen',
    'motif',
    'hole',
    'smell',
    'smart',
    'chaos',
    'fuel',
    'palace'
];

Unique Arrays

Take the following array, remove the duplicates, and return a new array. You're more than likely going to want to check out the indexOf function.

Do this in the form of a function uniquifyArray that receives an array of words as a parameter.

Starter Code

var words = [
  'crab',
  'poison',
  'contagious',
  'simple',
  'bring',
  'sharp',
  'playground',
  'poison',
  'communion',
  'simple',
  'bring'
];

Finding Elements

Let's create a simple array search.

Write a function doesWordExist 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

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

Counting Repetion

Write a function howManyTimes that will take in an array of words as one argument, and a word to search for as the other. The function will return the number of times that word appears in the array.

Starter Code

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

Bonus Quest

In the 20×20 grid below; What is the greatest product of four adjacent numbers in the same direction (up, down, left, right)?

Write a function greatestProduct to find the answer!

var matrix = [
  [08,02,22,97,38,15,00,40,00,75,04,05,07,78,52,12,50,77,91,08],
  [49,49,99,40,17,81,18,57,60,87,17,40,98,43,69,48,04,56,62,00],
  [81,49,31,73,55,79,14,29,93,71,40,67,53,88,30,03,49,13,36,65],
  [52,70,95,23,04,60,11,42,69,24,68,56,01,32,56,71,37,02,36,91],
  [22,31,16,71,51,67,63,89,41,92,36,54,22,40,40,28,66,33,13,80],
  [24,47,32,60,99,03,45,02,44,75,33,53,78,36,84,20,35,17,12,50],
  [32,98,81,28,64,23,67,10,26,38,40,67,59,54,70,66,18,38,64,70],
  [67,26,20,68,02,62,12,20,95,63,94,39,63,08,40,91,66,49,94,21],
  [24,55,58,05,66,73,99,26,97,17,78,78,96,83,14,88,34,89,63,72],
  [21,36,23,09,75,00,76,44,20,45,35,14,00,61,33,97,34,31,33,95],
  [78,17,53,28,22,75,31,67,15,94,03,80,04,62,16,14,09,53,56,92],
  [16,39,05,42,96,35,31,47,55,58,88,24,00,17,54,24,36,29,85,57],
  [86,56,00,48,35,71,89,07,05,44,44,37,44,60,21,58,51,54,17,58],
  [19,80,81,68,05,94,47,69,28,73,92,13,86,52,17,77,04,89,55,40],
  [04,52,08,83,97,35,99,16,07,97,57,32,16,26,26,79,33,27,98,66],
  [88,36,68,87,57,62,20,72,03,46,33,67,46,55,12,32,63,93,53,69],
  [04,42,16,73,38,25,39,11,24,94,72,18,08,46,29,32,40,62,76,36],
  [20,69,36,41,72,30,23,88,34,62,99,69,82,67,59,85,74,04,36,16],
  [20,73,35,29,78,31,90,01,74,31,49,71,48,86,81,16,23,57,05,54],
  [01,70,54,71,83,51,54,69,16,92,33,48,61,43,52,01,89,19,67,48],
];