3-get-card-value.js

// This problem involves playing cards: https://en.wikipedia.org/wiki/Standard_52-card_deck

// Implement a function getCardValue, when given a string representing a playing card,
// should return the numerical value of the card.

// A valid card string will contain a rank followed by the suit.
// The rank can be one of the following strings:
//   "A", "2", "3", "4", "5", "6", "7", "8", "9", "10", "J", "Q", "K"
// The suit can be one of the following emojis:
//   "♠", "♥", "♦", "♣"
// For example: "A♠", "2♥", "10♥", "J♣", "Q♦", "K♦".

// When the card is an ace ("A"), the function should return 11.
// When the card is a face card ("J", "Q", "K"), the function should return 10.
// When the card is a number card ("2" to "10"), the function should return its numeric value.

// When the card string is invalid (not following the above format), the function should
// throw an error.

// Acceptance criteria:
// After you have implemented the function, write tests to cover all the cases, and
// execute the code to ensure all tests pass.

function getCardValue(card) {
  // TODO: Implement this function

  // 1. Define valid suits and ranks
  const suits = ["♠", "♥", "♦", "♣"];
  const ranks = [
    "A",
    "2",
    "3",
    "4",
    "5",
    "6",
    "7",
    "8",
    "9",
    "10",
    "J",
    "Q",
    "K",
  ];

  // 2. Basic validation: ensure card is a string and not empty
  if (typeof card !== "string" || card.length === 0) {
    throw new Error("Card must be a non-empty string");
  }

  // 3. Extract rank and suit from the card string
  const rank = card.substring(0, card.length - 1);
  const suit = card.substring(card.length - 1);

  // 4. Validate rank and suit
  if (!ranks.includes(rank)) {
    throw new Error("Invalid rank");
  }
  if (!suits.includes(suit)) {
    throw new Error("Invalid suit");
  }

  // 5. Return the appropriate value based on the rank
  if (rank === "A") {
    return 11;
  } else if (["J", "Q", "K"].includes(rank)) {
    return 10;
  } else {
    return parseInt(rank);
  }
}

// The line below allows us to load the getCardValue function into tests in other files.
// This will be useful in the "rewrite tests with jest" step.
module.exports = getCardValue;

// Helper functions to make our assertions easier to read.
function assertEquals(actualOutput, targetOutput) {
  console.assert(
    actualOutput === targetOutput,
    `Expected ${actualOutput} to equal ${targetOutput}`
  );
}

// TODO: Write tests to cover all outcomes, including throwing errors for invalid cards.
// Examples:
assertEquals(getCardValue("9♠"), 9);

// Handling invalid cards
try {
  getCardValue("invalid");

  // This line will not be reached if an error is thrown as expected
  console.error("Error was not thrown for invalid card");
} catch (e) {}

// What other invalid card cases can you think of?

try {
  getCardValue("11♠");
  console.error("Error was not thrown for invalid rank");
} catch (e) {}

try {
  getCardValue("A♤");
  console.error("Error was not thrown for invalid suit");
} catch (e) {}

try {
  getCardValue("");
  console.error("Error was not thrown for empty string");
} catch (e) {}

try {
  getCardValue(123);
  console.error("Error was not thrown for non-string input");
} catch (e) {}

try {
  getCardValue("10");
  console.error("Error was not thrown for missing suit");
} catch (e) {}

try {
  getCardValue("♠");
  console.error("Error was not thrown for missing rank");
} catch (e) {}

try {
  getCardValue("A");
  console.error("Error was not thrown for missing suit");
} catch (e) {}

try {
  getCardValue("1♠");
  console.error("Error was not thrown for invalid rank");
} catch (e) {}

try {
  getCardValue("10XX");
  console.error("Error was not thrown for extra characters");
} catch (e) {}

try {
  getCardValue("Z♦");
  console.error("Error was not thrown for invalid rank");
} catch (e) {}