Simple Javascript Number Guessing Game (Free Download)

Welcome to a tutorial on how to create a simple Javascript number guessing game. So you have mastered the basics of Javascript and want to test out your newfound code ninja powers? Maybe take the first step into game development?

Well, this guide may not be what some of you guys are expecting – There are no graphics and no artificial intelligence programming here. But it does walk you through how to put the basics together to create a simple “hello world” game. Read on!

 

 

TABLE OF CONTENTS

 

 

NUMBER GUESSING GAME DEMO

Guesses – 0

 

 

PART 1) HTML INTERFACE

<form id="guess-wrap" onsubmit="return false;">
  <input id="guess-num" type="number" required min="0" max="100" value="0">
  <div id="guess-txt">
    <div id="guess-tries">Guesses - <i>0</i></div>
    <div id="guess-hint"></div>
  </div>
  <input id="guess-btn" type="submit" value="Make a Guess (0 to 100)">
</form>

That’s right, there are only a few components here.

• <input id="guess-num"> Number field to input the number.
• <div id="guess-tries"> The number of guesses so far.
• <div id="guess-hint"> Used to display hints, if the number is too high or too low.
• <input id="guess-btn"> “Make a guess” and “reset game” button.

 

 

PART 2) GAME INIT & PROPERTIES

var guess = {
  // (A) PROPERTIES
  // (A1) HTML ELEMENTS
  hform : null,  // number guess form
  hnum : null,   // number input field
  htries : null, // number of tries
  hhint : null,  // hint
  hbtn : null,   // guess/reset button
 
  // (A2) FLAGS
  min : 0,     // min allowed number
  max : 0,     // max allowed number
  jackpot : 0, // the correct number
  guesses : 0, // total nunmber of guesses made
 
  // (B) INITIALIZE
  init : () => {
    // (B1) GET HTML ELEMENTS
    guess.hform = document.getElementById("guess-wrap");
    guess.hnum = document.getElementById("guess-num");
    guess.htries = document.querySelector("#guess-tries i");
    guess.hhint = document.getElementById("guess-hint");
    guess.hbtn = document.getElementById("guess-btn");
 
    // (B2) MIN/MAX NUMBER
    guess.min = Math.ceil(guess.hnum.min);
    guess.max = Math.floor(guess.hnum.max);
 
    // (B3) RESET GAME
    guess.reset();
  },
  // ...
};
window.addEventListener("load", guess.init);

Not going to explain the Javascript line by line, but a quick summary.

• The entire game mechanics is contained within the var guess = {} object.
• (A) A whole bunch of game flags and properties.
  • (A1) References back to the HTML elements.
  • (A2) Game flags – The min/max allowed number, the current “Jackpot” number, and the total number of guesses.
• (B) On window load, init() will run. Pretty self-explanatory – Get all the HTML elements and reset the game.

 

 

PART 3) RESET GAME

// (C) RESET GAME
reset : () => {
  // (C1) RESET FLAGS
  guess.guesses = 0;
  // credits: https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Math/random
  guess.jackpot = Math.floor(Math.random() * (guess.max - guess.min + 1)) + guess.min;
  console.log("Jackpot - " + guess.jackpot); // for the cheaters
 
  // (C2) RESET HTML
  guess.hnum.value = guess.min;
  guess.hnum.readOnly = false;
  guess.htries.innerHTML = 0;
  guess.hhint.innerHTML = "";
  guess.hhint.className = "";
  guess.hbtn.value = `Make a Guess (${guess.min} to ${guess.max})`;
  guess.hform.onsubmit = () => guess.check();
  return false;
},

Next, guess.reset() is used to restart the game – Generate a new random “Jackpot” number, and reset the HTML interface.

 

 

PART 4) CHECK NUMBER

// (D) MAKE A GUESS
check : () => {
  // (D1) GET CHOSEN NUMBER + RESET CSS
  var num = +guess.hnum.value;
  guess.guesses++;
  guess.htries.innerHTML = guess.guesses;
  guess.hhint.classList.remove("high");
  guess.hhint.classList.remove("low");
 
  // (D2) HIT!
  if (num==guess.jackpot) {
    guess.hhint.innerHTML = "Nailed it!";
    guess.hhint.classList.add("hit");
    guess.hnum.readOnly = true;
    guess.hbtn.value = "Reset";
    guess.hform.onsubmit = () => guess.reset();
  }
 
  // (D3) MISS - GIVE HINTS
  else {
    // (D3-1) HIGHER OR LOWER?
    let difference = num - guess.jackpot, text = "";
    if (difference>0) {
      text = "high";
      guess.hhint.classList.add("high");
    } else {
      text = "low";
      guess.hhint.classList.add("low");
    }
 
    // (D3-2) TOO MUCH OR CLOSE?
    difference = Math.abs(difference);
    if (difference>20) {
      text = "Too " + text;
    } else if (difference>=10) {
      text = "Slightly " + text;
    } else {
      text = "A little " + text;
    }
 
    // (D3-3) INTERFACE UPDATE
    guess.hhint.innerHTML = text;
  }
  return false;
}

Lastly, guess.check() runs whenever the player enters a number. Seemingly confusing at first, but trace through the code – It simply checks against the “Jackpot” number and gives hints on whether the guess is too high/low… Or if it is a hit (win).

 

 

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EXAMPLE CODE DOWNLOAD

Click here for the source code on GitHub gist, just click on “download zip” or do a git clone. I have released it under the MIT license, so feel free to build on top of it or use it in your own project.

 

 

COMPATIBILITY CHECKS

• Arrow Function – CanIUse

This game does not use a lot of advanced features, will work on most modern browsers.

 

LINKS & REFERENCES

• Javascript BlackJack – Code Boxx
• Javascript MineSweeper – Code Boxx
• Javascript Hangman – Code Boxx
• Javascript Quiz – Code Boxx
• Javascript Memory Game – Code Boxx
• Javascript Number Guessing Game – Code Boxx
• Javascript Tic-Tac-Toe – Code Boxx
• Javascript Rock Paper Scissors Game – Code Boxx