Assignment 3

For this assignment, we will be taking a nice break from Express and Firebase to learn about some cool JavaScript/Typescript fundamentals!

ALL questions in this assignment MUST be done using .map, .filter, or .reduce. We will give you no credit for an approach that is not functional.

ALL functions must also be defined using arrow functions:

(params) => {
  // function body
};

You must write your functions from the starter code. You are not allowed to change the function signature.

Question 1

Write a function arrayMean that takes in an array of numbers and returns the mean. If the array is empty, return undefined.

Starter code:

export const arrayMean = (array: number[]): number | undefined => {
  /* TODO: add your code */
};

Example for myMean

arrayMean([1, 2, 3, 4, 5]); // 3
arrayMean([]); // undefined

Question 2

Write a function affordableHousing that takes in an array of Apartments and returns the list of ids of Apartments with rent less than or equal to budget.

Starter code:

type Apartment = {
  id: string;
  rent: number;
};

export const affordableHousing = (
  listings: Apartment[],
  budget: number,
): string[] => {
  /* TODO: add your code */
};

Example for affordableHousing

const apts: Apartment[] = [
  { id: 'orbis', rent: 5000 },
  { id: 'ereve', rent: 12345 },
  { id: 'henesys', rent: 1337 },
];

affordableHousing(apts, 5000); // ['orbis', 'henesys']
affordableHousing(apts, 4000); // ['henesys']

Question 3

Write a function evenEven that takes in an array of strings and returns true if every even-length string contains 'even' as a substring.

Starter code:

export const evenEven = (array: string[]): boolean => {
  /* TODO: add your code */
};

Example for evenEven

evenEven(['bob']); // true
evenEven(['bob', 'steven']); // true
evenEven(['bob', 'steven', 'even']); // true
evenEven(['bob', 'steven', 'anna']); // false

Question 4

Write a function makeSentences that takes in an array of objects in the format {name: string, age: number, breed: string} and maps it to an array of sentences in the format "name is age years old, and is a breed."

Please use object destructuring to get object fields.

NOTE

A "prototype" is an instance of an object in JavaScript/TypeScript. In documentation, methods are often denoted like: Type.prototype.method()

Remember, anything in JavaScript/TypeScript can be an object!

So, we can do: (5).toExponential(10) or let x = 5; x.toExponential()

Your goal is to round the age to the nearest tenth.

For example, you want to display "5.6 years" for the value 5.64 and "5.7 years" for the value 5.65.

Take a look at this documentation if you are stuck!

Example for makeSentences

const doggos = [
  { name: 'Sparky', age: 3.35, breed: 'Pomeranian Husky' },
  { name: 'Oreo', age: 5.42, breed: 'Dalmatian' },
  { name: 'Stella', age: 4, breed: 'Alaskan Klee Kai' },
];

makeSentences(doggos);

should output

[
  'Sparky is 3.4 years old and is a Pomeranian Husky',
  'Oreo is 5.4 years old and is a Dalmatian',
  'Stella is 4.0 years old and is a Alaskan Klee Kai',
];

Starter code:

// TODO: You should replace this any with an accurate object type in your submission!
type Doggo = any;

export const makeSentences = (array: Doggo[]): string[] => {
  /* TODO: add your code */
};

Don't worry about printing "year" vs "years" or "a" vs "an", unless you want the extra challenge!

Submission

Please submit to CMS your index.ts file containing your implementations of each of the functions described above.