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 rank = card.slice(0, -1); // Get the rank by slicing off the last character (the suit)
  const suit = card.slice(-1); // Get the suit by taking the last character of the string

  // Validate the suit
  const validSuits = ["♠", "♥", "♦", "♣"];
  if (!validSuits.includes(suit)) {
    throw new Error("Invalid card: Invalid suit");
  }
  // Determine the value based on the rank
  if (rank === "A") {
    return 11;
  } else if (["J", "Q", "K"].includes(rank)) {
    return 10;
  } else if (!isNaN(rank) && parseInt(rank) >= 2 && parseInt(rank) <= 10) {
    return parseInt(rank);
  } else {
    throw new Error("Invalid card: Invalid 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);
assertEquals(getCardValue("A♥"), 11);
assertEquals(getCardValue("J♦"), 10);
assertEquals(getCardValue("Q♣"), 10);
assertEquals(getCardValue("K♦"), 10);
assertEquals(getCardValue("10♥"), 10);

// Test invalid cards - these should throw errors
function testInvalidCard(card) {
  try {
    getCardValue(card);
    console.error(`Error was not thrown for invalid card: ${card}`);
  } catch (e) {
    console.log(`✓ Correctly threw error for: ${card}`);
  }
}

testInvalidCard("11♠"); // Invalid rank
testInvalidCard("A"); // Missing suit
testInvalidCard("2X"); // Invalid suit
testInvalidCard("invalid"); // Completely invalid
testInvalidCard(""); // Empty string
testInvalidCard("A♠♠"); // Extra character
testInvalidCard("1♠"); // Invalid rank (1 instead of A)
testInvalidCard("B♠"); // Invalid rank
testInvalidCard("A♠A"); // Invalid format