Add task file and tests

functions.js

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+/**************************************************************
+ * getBookById(bookId, books):
+ * - receives a bookId
+ * - recieves an array of book objects
+ * - returns the book object that matches that id
+ * - returns undefined if no matching book is found
+ ****************************************************************/
+function getBookById(bookId, books) {
+  // Your code goes here
+  // return books.find(book => book.id === bookId);
+}
+
+/**************************************************************
+ * getAuthorByName(authorName, authors):
+ * - receives an authorName
+ * - recieves an array of author objects
+ * - returns the author that matches that name (CASE INSENSITIVE)
+ * - returns undefined if no matching author is found
+ ****************************************************************/
+function getAuthorByName(authorName, authors) {
+  // Your code goes here
+  // return authors.find(
+  //   author => author.name.toLowerCase() === authorName.toLowerCase()
+  // );
+}
+
+/**************************************************************
+ * bookCountsByAuthor(authors):
+ * - receives an array of authors
+ * - returns an array of objects with the format:
+ *    [{ author: <NAME>, bookCount: <NUMBER_OF_BOOKS> }]
+ ****************************************************************/
+function bookCountsByAuthor(authors) {
+  // Your code goes here
+  // return authors.map(author => ({
+  //   author: author.name,
+  //   bookCount: author.books.length
+  // }));
+}
+
+/**************************************************************
+ * booksByColor(books):
+ * - receives an array of books
+ * - returns an object where the keys ar colors
+ *   and the values are arrays of book titles:
+ *    { <COLOR>: [<BOOK_TITLES>] }
+ ****************************************************************/
+function booksByColor(books) {
+  const colors = {};
+
+  // Your code goes here
+  // books.forEach(book => {
+  //   if (colors[book.color]) {
+  //     colors[book.color].push(book.title);
+  //   } else {
+  //     colors[book.color] = [book.title];
+  //   }
+  // });
+
+  return colors;
+}
+
+/**************************************************************
+ * titlesByAuthorName(authorName, authors, books):
+ * - receives an authorName
+ * - recieves an array of author objects
+ * - recieves an array of book objects
+ * - returns an array of the titles of the books written by that author:
+ *    ["The Hitchhikers Guide", "The Meaning of Liff"]
+ ****************************************************************/
+function titlesByAuthorName(authorName, authors, books) {
+  // Your code goes here
+  // const author = getAuthorByName(authorName, authors);
+  // if (!author) return [];
+  // return author.books.map(bookId => getBookById(bookId, books).title);
+}
+
+/**************************************************************
+ * mostProlificAuthor(authors):
+ * - receives a list of authors
+ * - returns the name of the author with the most books
+ *
+ * Note: assume there will never be a tie
+ ****************************************************************/
+function mostProlificAuthor(authors) {
+  // Your code goes here
+  // let prolificAuthor = authors[0];
+  // authors.forEach(author => {
+  //   if (author.books.length > prolificAuthor.books.length) {
+  //     prolificAuthor = author;
+  //   }
+  // });
+  // return prolificAuthor.name;
+  /* One-liner using reduce and a ternary operator */
+  // return authors.reduce((a, b) => (a.books.length > b.books.length ? a : b))
+  //   .name;
+}
+
+/**************************************************************
+ * relatedBooks(bookId, books):
+ * - receives a bookId
+ * - receives a list of authors
+ * - receives a list of books
+ * - returns a list of the titles of all the books by
+ *   the same author as the book with bookId
+ *   (including the original book)
+ *
+ * NOTES: YOU NEED TO TAKE INTO ACCOUNT BOOKS WITH MULTIPLE AUTHORS
+ * BONUS: REMOVE DUPLICATE BOOKS
+ ****************************************************************/
+function relatedBooks(bookId, authors, books) {
+  // Your code goes here
+  // const book = getBookById(bookId, books);
+  // let titles = [];
+  // book.authors.forEach(
+  //   author =>
+  //     (titles = titles.concat(titlesByAuthorName(author.name, authors, books)))
+  // );
+  // /* BONUS */
+  // // titles = [...new Set(titles)];
+  // return titles;
+  /* "One-liner" using reduce */
+  // return getBookById(bookId, books).authors.reduce(
+  //   (titles, author) => [
+  //     ...new Set(titles.concat(titlesByAuthorName(author.name, authors, books)))
+  //   ],
+  //   []
+  // );
+}
+
+/**************************************************************
+ * friendliestAuthor(authors):
+ * - receives a list of authors
+ * - returns the name of the author that has
+ *   co-authored the greatest number of books
+ ****************************************************************/
+function friendliestAuthor(authors) {
+  // authors.forEach(author => {
+  //   author.coauthoringCount = 0;
+  //   authors.forEach(secondAuthor => {
+  //     if (secondAuthor.name !== author.name) {
+  //       const sharedBooks = secondAuthor.books.filter(bookId =>
+  //         author.books.includes(bookId)
+  //       );
+  //       author.coauthoringCount += sharedBooks.length;
+  //     }
+  //   });
+  // });
+  // let friendlyAuthor = authors[0];
+  // authors.forEach(author => {
+  //   if (author.coauthoringCount > friendlyAuthor.coauthoringCount) {
+  //     friendlyAuthor = author;
+  //   }
+  // });
+  // return friendlyAuthor.name;
+}
+
+module.exports = {
+  getBookById,
+  getAuthorByName,
+  bookCountsByAuthor,
+  booksByColor,
+  titlesByAuthorName,
+  mostProlificAuthor,
+  relatedBooks,
+  friendliestAuthor
+};
+
+/**
+ * Uncomment the following lines if you
+ * want to manually test your code
+ */
+
+// const authors = require("./authors.json");
+// const books = require("./books.json");
+
+// console.log(getBookById(12, books));
+// console.log(getAuthorByName("J.K. Rowling", authors));
+// console.log(bookCountsByAuthor(authors));
+// console.log(booksByColor(books));
+// console.log(titlesByAuthorName("George R.R. Martin", authors, books));
+// console.log(mostProlificAuthor(authors));
+// console.log(relatedBooks(50, books));
+// console.log(friendliestAuthor(authors));

functions.spec.js

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+/**************************
+ *
+ * THIS IS A TESTING FILE
+ *
+ * DO NOT MODIFY THIS FILE
+ *
+ ***************************/
+
+import {
+  getBookById,
+  getAuthorByName,
+  bookCountsByAuthor,
+  booksByColor,
+  titlesByAuthorName,
+  mostProlificAuthor,
+  relatedBooks,
+  friendliestAuthor
+} from "./functions";
+
+// Data
+import authors from "./authors.json";
+import books from "./books.json";
+
+describe("getBookById(bookId, books)", () => {
+  test("returns the correct book", () => {
+    const expected = books[Math.floor(Math.random() * books.length)];
+    const result = getBookById(expected.id, books);
+    expect(result).toBe(expected);
+  });
+
+  test("returns undefined if the book is not found", () => {
+    const result = getBookById(10000, books);
+    expect(result).toBeUndefined();
+  });
+});
+
+describe("getAuthorByName(authorName, authors)", () => {
+  test("returns the correct author", () => {
+    const expected = authors[Math.floor(Math.random() * authors.length)];
+    const result = getAuthorByName(expected.name, authors);
+    expect(result).toBe(expected);
+  });
+
+  test("is case insensitive", () => {
+    const expected = authors[Math.floor(Math.random() * authors.length)];
+    let result = getAuthorByName(expected.name.toLowerCase(), authors);
+    expect(result).toBe(expected);
+    result = getAuthorByName(expected.name.toUpperCase(), authors);
+    expect(result).toBe(expected);
+  });
+
+  test("returns undefined if the author is not found", () => {
+    const result = getAuthorByName("Dr Patatis", authors);
+    expect(result).toBeUndefined();
+  });
+});
+
+describe("bookCountsByAuthor(authors)", () => {
+  test("returns the correct number of objects", () => {
+    const expected = authors.length;
+    const result = bookCountsByAuthor(authors).length;
+    expect(result).toBe(expected);
+  });
+
+  test("returns the correct format", () => {
+    const result = bookCountsByAuthor(authors).every(author => {
+      const keys = Object.keys(author);
+      return keys.includes("author") && keys.includes("bookCount");
+    });
+    expect(result).toBe(true);
+  });
+
+  test("returns the correct data", () => {
+    const expected = [
+      { author: "Margaret Atwood", bookCount: 4 },
+      { author: "Lauren Beukes", bookCount: 2 }
+    ];
+    const result = bookCountsByAuthor(authors.slice(0, 2));
+    expect(result).toEqual(expected);
+  });
+});
+
+describe("booksByColor(books)", () => {
+  test("returns the correct number of colors", () => {
+    const expected = 2;
+    const onlyGreenAndBlueBooks = books.filter(
+      book => book.color === "green" || book.color === "blue"
+    );
+    const result = Object.keys(booksByColor(onlyGreenAndBlueBooks)).length;
+    expect(result).toBe(expected);
+  });
+
+  test("returns the correct format", () => {
+    const result = Object.values(booksByColor(books)).every(bookList =>
+      Array.isArray(bookList)
+    );
+    expect(result).toBe(true);
+  });
+
+  test("returns the correct data", () => {
+    const expected = {
+      white: [
+        "12 Rules for Life: An Antidote to Chaos",
+        "A Dance With Dragons"
+      ],
+      yellow: ["A Clash of Kings"],
+      red: ["A Feast for Crows"]
+    };
+    const result = booksByColor(books.slice(0, 4));
+    expect(result).toEqual(expected);
+  });
+});
+
+describe("titlesByAuthorName(authorName, authors, books)", () => {
+  test("returns the correct list of books", () => {
+    let expected = ["The Shining Girls", "Zoo City"].sort();
+    let result = titlesByAuthorName("Lauren Beukes", authors, books).sort();
+    expect(result).toEqual(expected);
+    expected = ["Jane Eyre"];
+    result = titlesByAuthorName("Charlotte Brontë", authors, books);
+    expect(result).toEqual(expected);
+  });
+
+  test("is case-insensitive", () => {
+    let expected = ["The Shining Girls", "Zoo City"].sort();
+    let result = titlesByAuthorName("LaUreN BEukeS", authors, books).sort();
+    expect(result).toEqual(expected);
+    expected = ["Jane Eyre"];
+    result = titlesByAuthorName("CHaRlOttE BRontë", authors, books);
+    expect(result).toEqual(expected);
+  });
+
+  test("returns an empty array if the author is not found", () => {
+    const result = titlesByAuthorName("Dr Patatis", authors, books);
+    expect(result).toEqual([]);
+  });
+});
+
+describe("mostProlificAuthor(authors)", () => {
+  test("returns the correct author name", () => {
+    const expected = "Agatha Christie";
+    const result = mostProlificAuthor(authors.slice(0, 5));
+    expect(result).toBe(expected);
+  });
+});
+
+describe("relatedBooks(bookId, authors, books)", () => {
+  test("returns the correct books", () => {
+    const expected = ["The Shining Girls", "Zoo City"].sort();
+    const result = relatedBooks(37, authors, books).sort();
+    expect(result).toEqual(expected);
+  });
+
+  test("can handle co-authored books - returns the titles of books by BOTH authors", () => {
+    const expected = [
+      "Good Omens",
+      "Good Omens",
+      "Neverwhere",
+      "Coraline",
+      "The Color of Magic",
+      "The Hogfather",
+      "Wee Free Men",
+      "The Long Earth",
+      "The Long War",
+      "The Long Mars"
+    ].sort();
+    const result = relatedBooks(46, authors, books).sort();
+    expect(result).toEqual(expected);
+  });
+
+  /**
+   * Remove the x to unskip and run the bonus test.
+   * Add an x to the previous test to skip it
+   */
+  xtest("BONUS - removes duplicate books", () => {
+    const expected = [
+      "Good Omens",
+      "Neverwhere",
+      "Coraline",
+      "The Color of Magic",
+      "The Hogfather",
+      "Wee Free Men",
+      "The Long Earth",
+      "The Long War",
+      "The Long Mars"
+    ].sort();
+    const result = relatedBooks(46, authors, books).sort();
+    expect(result).toEqual(expected);
+  });
+});
+
+describe("friendliestAuthor(authors)", () => {
+  test("returns the correct author", () => {
+    const expected = "Terry Pratchett";
+    const result = friendliestAuthor(authors);
+    expect(result).toEqual(expected);
+  });
+});