Pure JavaScript A* maze solving – with a bit of magic thanks to Phaser and EasyStar.js updated to Phaser 3.8.0 and EasyStar.js 0.4.3

During these days I am working on a project which requires A* algorithm for path finding, so I grabbed my 3 years old post “Pure JavaScript A* maze solving – with a bit of magic thanks to Phaser and EasyStar.js” and updated to the latest Phaser and EasyStar versions. Here is a maze, solved by A* algorithm, going from the top left cell to the bottom right cell. Once a maze is solved, a new random maze is generated and solved again, and so on.

I am using the awesome EasyStar.js to solve the maze. If you want more information about maze generation, refer to the post “Pure JavaScript perfect tile maze generation – with a bit of magic thanks to Phaser“. If you are interested in the source code, here it is:

var game;

var gameOptions = {
    mazeWidth: 81,
    mazeHeight: 61,
    tileSize: 10
}

window.onload = function() {
    var gameConfig = {
       type: Phaser.CANVAS,
       width: gameOptions.mazeWidth * gameOptions.tileSize,
       height: gameOptions.mazeHeight * gameOptions.tileSize,
       backgroundColor: 0xaaaaaa,
       scene: [playGame]
    };
    game = new Phaser.Game(gameConfig);
    window.focus()
    resize();
    window.addEventListener("resize", resize, false);
}

class playGame extends Phaser.Scene{
    constructor(){
        super("PlayGame");
    }
    create(){
        this.mazeGraphics = this.add.graphics();
        var moves = [];
        this.maze = [];
        for(var i = 0; i < gameOptions.mazeHeight; i ++){
            this.maze[i] = [];
            for(var j = 0; j < gameOptions.mazeWidth; j ++){
                this.maze[i][j] = 1;
            }
        }
        var posX = 1;
        var posY = 1;
        this.maze[posX][posY] = 0;
        moves.push(posY + posY * gameOptions.mazeWidth);
        while(moves.length){
            var possibleDirections = "";
            if(posX+2 > 0 && posX + 2 < gameOptions.mazeHeight - 1 && this.maze[posX + 2][posY] == 1){
                possibleDirections += "S";
            }
            if(posX-2 > 0 && posX - 2 < gameOptions.mazeHeight - 1 && this.maze[posX - 2][posY] == 1){
                possibleDirections += "N";
            }
            if(posY-2 > 0 && posY - 2 < gameOptions.mazeWidth - 1 && this.maze[posX][posY - 2] == 1){
                possibleDirections += "W";
            }
            if(posY+2 > 0 && posY + 2 < gameOptions.mazeWidth - 1 && this.maze[posX][posY + 2] == 1){
                possibleDirections += "E";
            }
            if(possibleDirections){
                var move = Phaser.Math.Between(0, possibleDirections.length - 1);
                switch (possibleDirections[move]){
                    case "N":
                        this.maze[posX - 2][posY] = 0;
                        this.maze[posX - 1][posY] = 0;
                        posX -= 2;
                        break;
                    case "S":
                        this.maze[posX + 2][posY] = 0;
                        this.maze[posX + 1][posY] = 0;
                        posX += 2;
                        break;
                    case "W":
                        this.maze[posX][posY - 2] = 0;
                        this.maze[posX][posY - 1] = 0;
                        posY -= 2;
                        break;
                    case "E":
                        this.maze[posX][posY + 2] = 0;
                        this.maze[posX][posY + 1] = 0;
                        posY += 2;
                        break;
                }
                moves.push(posY + posX * gameOptions.mazeWidth);
            }
            else{
                var back = moves.pop();
                posX = Math.floor(back / gameOptions.mazeWidth);
                posY = back % gameOptions.mazeWidth;
            }
        }
        this.drawMaze(posX, posY);
        var easystar = new EasyStar.js();
        easystar.setGrid(this.maze);
        easystar.setAcceptableTiles([0]);
        easystar.findPath(1, 1, gameOptions.mazeWidth - 2, gameOptions.mazeHeight - 2, function(path){
            this.drawPath(path);
        }.bind(this));
        easystar.calculate();
    }
    drawMaze(posX, posY){
        this.mazeGraphics.fillStyle(0x000000);
        for(var i = 0; i < gameOptions.mazeHeight; i ++){
            for(var j = 0; j < gameOptions.mazeWidth; j ++){
                if(this.maze[i][j] == 1){
                    this.mazeGraphics.fillRect(j * gameOptions.tileSize, i * gameOptions.tileSize, gameOptions.tileSize, gameOptions.tileSize);
                }
            }
        }
    }
    drawPath(path){
        var i = 0;
        this.time.addEvent({
            delay: 5,
            callback: function(){
                if(i < path.length){
                    this.mazeGraphics.fillStyle(0x660000);
                    this.mazeGraphics.fillRect(path[i].x * gameOptions.tileSize + 1, path[i].y * gameOptions.tileSize + 1, gameOptions.tileSize - 2, gameOptions.tileSize - 2);
                    i++;
                }
                else{
                    this.scene.start("PlayGame");
                }
            },
            callbackScope: this,
            loop: true
        });
    }
}
function resize() {
    var canvas = document.querySelector("canvas");
    var windowWidth = window.innerWidth;
    var windowHeight = window.innerHeight;
    var windowRatio = windowWidth / windowHeight;
    var gameRatio = game.config.width / game.config.height;
    if(windowRatio < gameRatio){
        canvas.style.width = windowWidth + "px";
        canvas.style.height = (windowWidth / gameRatio) + "px";
    }
    else{
        canvas.style.width = (windowHeight * gameRatio) + "px";
        canvas.style.height = windowHeight + "px";
    }
}

Next time I’ll show you a little RPG engine using A* algorithm, meanwhile download the source code.