Sample code

 

Game Code

var game = {
    // Initialize game objects, preload assets and display start screen
    init: function() {
        // Get the canvas and its 2D context
        game.canvas = document.getElementById("gameCanvas");
        game.context = game.canvas.getContext("2d");
        
        // Hide all game layers and display the start screen
        game.hideScreens();
        game.showScreen("gamestartscreen");
    },
    
    hideScreens: function() {
        var screens = document.getElementsByClassName("gamelayer");
        
        // Iterate through all game layers and set their display to none
        for(let i = screens.length - 1; i >= 0; i--) {
            screens[i].style.display = "none";
        }
    },
    
    hideScreen: function(id) {
        var screen = document.getElementById(id);
        screen.style.display = "none";
    },
    
    showScreen: function(id) {
        var screen = document.getElementById(id);
        screen.style.display = "block";
    }
};

window.addEventListener("load", function() {
    game.init();
});