【JavaScript】canvas实现一个小游戏

参考：

1、image onload事件：http://www.runoob.com/jsref/event-img-onload.html（赞）

2、canvas的drawImage无法显示图像：https://segmentfault.com/q/1010000002877796

(尝试setInterval(render, 10);就会发现图片显示出来了。)

3、addeventlistener的捕获与冒泡：https://my.oschina.net/u/867090/blog/387380

4、取整方案：http://www.cnblogs.com/pigtail/archive/2012/03/28/2421614.html

5、二维数组：http://www.cnblogs.com/ymwangel/p/5875081.html

5、发现网上已经有很多人写了：http://www.qdfuns.com/notes/13275/a66ea9c091c5cc4d0007abaf83d223ca:storey-21

6、随机迷宫算法：随机迷宫算法、http://bbs.9ria.com/thread-156150-1-1.html

mytest.js

// Create the canvas
var canvas = document.createElement("canvas");
var ctx = canvas.getContext("2d");
canvas.width = 800;
canvas.height = 550;

canvas.style.position = "absolute";
canvas.style.left = "calc(50% - 350px)";
canvas.style.top = "calc(50% - 275px)";

document.body.appendChild(canvas);

// load images
var bgImage = new Image();
bgImage.src = "images/background.png";

var heroImage = new Image();
heroImage.src = "images/hero.png";

var wallImage = new Image();
wallImage.src = "images/wall.png";

// Game data
var hero = {
    x: 0,
    y: 0
};

var aa = new Array(); //定义一维数组
for(i = -1; i <= 14; i++) {
    aa[i] = new Array(); //将每一个子元素又定义为数组
    for(j = -1; j <= 13; j++) {
        aa[i][j] = false;
    }
} 

var x2 = 0;
var y2 = 0;
var notWall = function(x , y) {
    return !aa[x][y];
}

// random labyrinth

// Game data init
var reset = function() {
    // hero init
    hero.x = 100;
    hero.y = 100;

    // wall init
    for(i = 0; i <= 13; i++) {
        for(j = 0; j <= 12; j++) {
            aa[i][j] = Math.random() > 0.5 ? true : false;
        }
    }
}

// Game expression
var render = function() {
    // draw background
    ctx.drawImage(bgImage, 0, 0, 800, 550);

    // draw hero
    ctx.drawImage(heroImage, hero.x, hero.y);

    // draw wall
    for (m = 0; m <= 13; ++m)
        for (n = 0; n <=  12; ++n)
            if (aa[m][n]) ctx.drawImage(wallImage, 50*m+60, 36.5*n+40);
    ctx.fillText("hero positon: x=" + hero.x + ",y=" + hero.y, 100, 100);
}

var speed = 4;
addEventListener("keydown", function (e) {
    x2 = Math.floor((hero.x-44)/50);
    y2 = Math.floor((hero.y-32)/34.9);
    if (e.key == "ArrowUp" && hero.y > 32 && notWall(x2 , y2-1)) {
        hero.y -= speed;
    }
    if (e.key == "ArrowDown" && hero.y < canvas.height - 73 && notWall(x2 , y2+1)) {
        hero.y += speed;
    }
    if (e.key == "ArrowLeft" && hero.x > 44 && notWall(x2-1 , y2)) {
        hero.x -= speed;
    }
    if (e.key == "ArrowRight" && hero.x < canvas.width - 73 && notWall(x2+1 , y2)) {
        hero.x += speed;
    }
}, false);

var testGame = function() {
    reset();
      setInterval(render, 13);
}

testGame();