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
  const cardRanks = [
    "A",
    "2",
    "3",
    "4",
    "5",
    "6",
    "7",
    "8",
    "9",
    "10",
    "J",
    "Q",
    "K",
  ];
  const cardSuits = ["♠", "♥", "♦", "♣"];
  if (
    typeof card !== "string" ||
    !cardRanks.includes(card.slice(0,-1)) ||
    !cardSuits.includes(card.slice(-1))
  ) {
    throw new Error("Invalid card");
  }

  switch (card.slice(0, -1)) {
    case "A":
      return 11;
    case "J":
    case "Q":
    case "K":
      return 10;
    default:
      return Number(card.slice(0, -1));
  }
}



// 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);
assertEquals(getCardValue("A♥"), 11);
assertEquals(getCardValue("J♥"), 10);
assertEquals(getCardValue("Q♦"), 10);
assertEquals(getCardValue("K♣"), 10);
assertEquals(getCardValue("10♠"), 10);
assertEquals(getCardValue("5♠"), 5);

// 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) {}

try {
  getCardValue("A");
  console.error("Expected error for 'A' but none was thrown");
} catch (e) {}

try {
  getCardValue("♠");
  console.error("Expected error for '♠' but none was thrown");
} catch (e) {}

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