H5 canvas实现贪吃蛇小游戏

//给定初始位置向右(同keyCode右箭头)
this.direction = 39;
}
//画蛇的方法
Snake.prototype.draw = function () {
for (var i = 0; i < this.snakeArray.length; i++) {
this.snakeArray[i].draw();
}
}
//蛇移动的方法
Snake.prototype.move = function () {

//此处是核心部分，蛇的 移动方式
//1、画一个灰色的方块，位置与蛇头重叠
//2、将这个方块插到数组中蛇头后面一个的位置
//3、砍去末尾的方块
//4、将蛇头向设定方向移动一格
var rect = new Rect(this.head.x,this.head.y,this.head.w,this.head.h,"gray");
this.snakeArray.splice(1,0,rect);

//判断是否吃到食物，isEat判定函数写在最后了
//吃到则食物重新给位置，不砍去最后一节，即蛇变长
//没吃到则末尾砍掉一节，即蛇长度不变
if (isEat()){
food = new getRandomFood();
}else{
this.snakeArray.pop();
}

//设置蛇头的运动方向，37 左，38 上，39 右，40 下
switch (this.direction) {
case 37:
this.head.x -= this.head.w
break;
case 38:
this.head.y -= this.head.h
break;
case 39:
this.head.x += this.head.w
break;
case 40:
this.head.y += this.head.h
break;
default:
break;
}

// gameover判定
// 撞墙
if (this.head.x > canvas.width || this.head.x < 0 || this.head.y > canvas.height || this.head.y < 0){
clearInterval(timer);
}

// 撞自己，循环从1开始，避开蛇头与蛇头比较的情况
for (var i = 1; i < this.snakeArray.length; i++) {
if (this.snakeArray[i].x == this.head.x && this.snakeArray[i].y == this.head.y){
clearInterval(timer);
}
}
}

//画出初始的蛇
var snake = new Snake()
snake.draw();

//画出初始的食物
var food = new getRandomFood()

//定时器
var timer = setInterval(function () {
context.clearRect(0,0,canvas.width,canvas.height);
food.draw();
snake.move();
snake.draw();
}, 100)

//键盘事件，其中的if判定是为了让蛇不能直接掉头
document.onkeydown = function (e) {
var ev = e||window.event;
switch(ev.keyCode){
case 37:{
if (snake.direction !== 39){
snake.direction = 37;
}
break;
}
case 38:{
if (snake.direction !== 40){
snake.direction = 38;
}
break;
}
case 39:{
if (snake.direction !== 37){
snake.direction = 39;
}
break;
}
case 40:{
if (snake.direction !== 38){
snake.direction = 40;
}
break;
}
}
ev.preventDefault();
}

//随机函数，获得[min,max]范围的值
function getNumberInRange (min,max) {
var range = max-min;
var r = Math.random();
return Math.round(r*range+min)
}

//构建食物对象