Exercise variables

  • 3 minutes

As a newly hired game developer, you've been tasked with building recreational games for the web. Your first assignment is to start working on the card game Texas Hold'em. Instead of having players bet money, you'll use points to represent poker chips.

Model the game state

You need to take what you know of Texas Hold'em and create variables to store card values. In doing so, you need to think about starter values and values that will change over time.

You know that Texas Hold'em features players, starter cards, and points. Try to scaffold a basic game structure by using variables.

  1. Create a file named app.js:

    touch app.js
code .

    You should now have an editor open in the shell.

  2. Add the following code to the file:

    let startingPokerChips = 100; // points
let players = 3;
let noOfStarterCards = 2;

    You now have three variables to represent the initial state of the game.

  3. Create variables that represent specific players. Add the following code:

    let playerOnePoints = startingPokerChips;
let playerTwoPoints = startingPokerChips;
let playerThreePoints = startingPokerChips;

    You've created three players' starting points by assigning them the variable startingPokerChips, which holds the value 100.

  4. Show a specific game round and how an assignment can represent a game state. Add the following lines to the code:

    playerOnePoints -= 50;
playerTwoPoints -=25;
playerThreePoints +=75;

You've successfully simulated a game round in which the first and second player bet 50 and 25 points, respectively. Because the third player has a better hand, they end up winning the game round. The game takes points from the first and second player and adds them to the pot of the third player.

Refactor to constants

At this point, you have some variables that represent parts of your card game. Remember that you have constants available, which are variables that shouldn't change their value. Let's see what variables might lend themselves to be better represented as constants in your source code.

Tip

Spend one to two minutes thinking about what variables shouldn't change and what variables might have changing values. Then scroll down to see the solution.

  1. At the top of the file, change the following code:

    let startingPokerChips = 100; // points
let players = 3;
let noOfStarterCards = 2;

    ...to this code:

    const STARTING_POKER_CHIPS = 100; // points
const PLAYERS = 3;
const NO_OF_STARTER_CARDS = 2;

    You've successfully identified which variables are important for the game. They also describe how the game is played. A player's starting poker chips will not change, even if a specific player's pot changes as they play. The number of players is also constant, unless you imagine that you might rebuild the game such that a player can join at any time. The number of starter cards is always two in Texas Hold'em. As the game developer, you have the power to decide ultimately what should be changeable and what should be constant.

    Tip

    A great way to think about variables is to make all variables constant to begin with. Then, decide if a variable's value will need to change in the future. In that case, change it from const to let.

  2. Be sure to change dependent code, so the code still compiles:

    let playerOnePoints = STARTING_POKER_CHIPS;
let playerTwoPoints = STARTING_POKER_CHIPS;
let playerThreePoints = STARTING_POKER_CHIPS;

Congratulations! You've started working on a JavaScript code base that implements Texas Hold'em. In doing so, you've reasoned through what the starter values are, what values can change, and how to change values.