原生javascript制作贪吃蛇小游戏

HTML部分

    
    
    


    
        游戏玩法：上下左右控制小蛇的方向。
        撞到边缘游戏结束。
        长按方向键即可加速。
    
    

        

        

        

    

//js开始

function $(id){
        return document.getElementById(id);
    }

    window.onload = function () {
        // 创建背景
        js_background();
        // 随机食物
        js_food();
        // 创建贪吃蛇
        create_snake();

        document.onkeydown = function(event){
            let evt = event || window.event;
            switch (evt.keyCode) {
                case 37:direction="left";break;
                case 38:direction="up";break;
                case 39:direction="right";break;
                case 40:direction="down";break;
                default:;
                // console.log(evt.keyCode);
            }
            start_snake()
        }

    }

// 贪吃蛇方向// 创建背景

// 贪吃蛇方向// 创建背景
    var direction = "right";
    // 创建背景
    function js_background(){
        let bg = document.createElement("div");
        bg.id = "js_bg";
        bg.style.cssText = "position:relative;margin :50px auto; background:skyblue; width:800px; height:600px;";
        document.body.appendChild(bg);
    }

// 随机食物

var food_left = 0;
    var food_top = 0;
    function js_food(){
        food_left = parseInt(Math.random()*800/20)*20;
        food_top = parseInt(Math.random()*600/20)*20;
        let foodDiv = document.createElement("div");
        foodDiv.style.cssText = "position:absolute;width:20px; height: 20px; border-radius:50%; background:yellow;";
        foodDiv.style.left = food_left+"px";
        foodDiv.style.top = food_top+"px";
        foodDiv.id = "foodDiv";
        $("js_bg").appendChild(foodDiv);

    }

// 创建贪吃蛇

function create_snake(){
        let lis = document.getElementsByTagName("li");
        lis[0].style.backgroundColor = "black";
        lis[0].style.zIndex = 1;
        for(let i = 0; i < lis.length; i++){
            lis[i].style.left = 280-(i*20)+"px";
            lis[i].style.top = 60+"px";
        }
    }

//定时器

    // 定时器
    let timre = setInterval(start_snake,200);
    let lis = document.getElementsByTagName("li");
    function start_snake(){
        let left=parseFloat(lis[0].style.left);
        let top= parseFloat(lis[0].style.top);
        // console.log(top)

        switch (direction) {
            case "left":left = (left-20);break;
            case "up":top = (top-20);break;
            case "right":left = (left+20);break;
            case "down":top = (top+20);break;
            default:;
        }

        if(left<0 || left>800-20 || top<0 || top>600-20){

                window.clearInterval(timre);
                alert("亲，您Game Over");
                return;
        }

        // for(let i = 1; i <= lis.length-1; i++){
        //     lis[i].style.left = lis[i-1].style.left;
        //     lis[i].style.top = lis[i-1].style.top;
        // }
        for(var i=lis.length-1;i>0;i--){
            lis[i].style.left = lis[i-1].style.left;
            lis[i].style.top = lis[i-1].style.top;
        }



        // 改变第一节
        lis[0].style.left  = left+"px";
        lis[0].style.top  = top+"px";

        // console.log(food_top+"----------");
        // console.log(top);

        if(left == food_left && top == food_top){
            eat();
        }
    }

    function eat() {
        $("js_bg").removeChild($("foodDiv"));
        js_food();
        // alert("ll");
        let li = document.createElement("li");
        $("js_bg").appendChild(li);
        // create_snake();


    }