原生JS贪吃蛇小游戏

思路：在页面上添加一个地图，以提供边界，在地图中随机出现食物，给蛇身设置一个初始长度，用键盘方向键控制蛇的走向，当蛇触碰到食物时（既坐标重复时），增加蛇身长度，碰到墙壁或自身时，程序停止，游戏结束。

HTML结构：

<body>
    <div id="map"></div>
</body>

CSS样式：

<style>
    #map{
        width: 600px;
        height: 300px;
        background: #ccc;
        border: 5px solid blacks;
        margin: 0 auto;
        position: relative;}
</style>

js实现功能：

<script>
    class Map{    //地图
        constructor(){
            this.mapEle = document.getElementById("map");
            this.w = this.mapEle.offsetWidth;
            this.h = this.mapEle.offsetHeight;
        }
    }
    class Food{    //食物
        constructor(){
            this.w = 20;
            this.h = 20;
            this.x = 0;
            this.y = 0;
            this.c = "orange";
            this.createEle();
        } 
        createEle(){
            this.foodEle = document.createElement("div");
            this.foodEle.style.cssText =  `width:${this.w}px;height:${this.h}px;background:${this.c};position:absolute;left:${this.x * this.w}px;top:${this.y * this.h}px;border-radius: 40%;`;
            m.mapEle.appendChild(this.foodEle);
        }
        randomPos(){
            this.x = random(0,(m.w-this.w) / this.w);
            this.y = random(0,(m.h-this.h) / this.h);
            this.foodEle.style.left = this.x * this.w + "px";
            this.foodEle.style.top = this.y * this.h + "px";
        }
    }
    class Snake{    //身体
        constructor(){
            this.w = 20;
            this.h = 20;
            this.body = [{
                 ele:null,x:4,y:3,c:randomColor()
            },{
                ele:null,x:3,y:3,c:randomColor()
            },{
                ele:null,x:2,y:3,c:randomColor()
            }];
            this.d = "right";   //设置默认行走方向
            this.createEle();
        }
        createEle(){
            for(var i=0;i<this.body.length;i++){
                if(!this.body[i].ele){
                    this.body[i].ele = document.createElement("div");
                    m.mapEle.appendChild(this.body[i].ele);
                }
                this.body[i].ele.style.cssText = `width:${this.w}px;height:${this.h}px;background:${this.body[i].c};position:absolute;left:${this.body[i].x * this.w}px;top:${this.body[i].y * this.h}px;color:#fff;border-radius: 40%;`;
            }
            this.body[0].ele.innerHTML = "00"
            setTimeout(()=>{this.move()},300);
        }
        move(){
            for(var i=this.body.length-1;i>0;i--){
                this.body[i].x = this.body[i-1].x;
                this.body[i].y = this.body[i-1].y;
            }
            switch(this.d){
                case "left":this.body[0].x -= 1;break;
                case "right":this.body[0].x += 1;break;
                case "top":this.body[0].y -= 1;break;
                case "bottom":this.body[0].y += 1;break;
            }
            if(this.body[0].x < 0 || this.body[0].y < 0 || this.body[0].x > ((m.w-this.w) / this.w) || this.body[0].y > ((m.h-this.h) / this.h)){
                alert("撞墙了");
                return;
            }
            if(this.body[0].x === f.x && this.body[0].y === f.y){
                this.body.push({ele:null,x:this.body[this.body.length-1].x,y:this.body[this.body.length-1].y,c:randomColor()});
                f.randomPos();
            }
            for(var i=1;i<this.body.length;i++){
                if(this.body[0].x == this.body[i].x && this.body[0].y == this.body[i].y){
                    alert("撞到自己了");
                    return;
                }
            }
            this.createEle();
        }
        direct(type){
            switch(type){
                case 37:
                    if(this.d === "right") break;
                    this.d = "left";break;
                case 38:
                    if(this.d === "bottom") break;
                    this.d = "top";break;
                case 39:
                    if(this.d === "left") break;
                    this.d = "right";break;
                case 40:
                    if(this.d === "top") break;
                    this.d = "bottom";break;
            }
        }
    }
    function random(a,b){
        return Math.round(Math.random()*(a-b)+b);
    }
    function randomColor(){
        return `rgb(${random(0,255)},${random(0,255)},${random(0,255)})`;
    }

    var m = new Map();

    var f = new Food();
    f.randomPos();

    var s = new Snake();
    document.onkeydown = function(eve){
        var e = eve || window.event;
        var code = e.keyCode || e.which;
        s.direct(code);
    }
</script>

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