最近初学JavaScript，在这里分享贪吃蛇小游戏的实现过程，
希望能看到的前辈们能指出这个程序的不足之处。
##大致思路
- 首先要解决的问题
- 随着蛇头的前进，尾巴也要前进。
- 用键盘控制蛇的运动方向。
- 初始化食物的时候不能初始化到蛇的身体上。
- 蛇吃食物的时候身体会变长。
- 蛇头碰到“墙”，或者自己的身体游戏结束
- 不影响游戏的实现但是有关于游戏体验的设计
- 界面的美观。
- 分数的设置。
- 等级的设置（随着分数的增加，蛇前进的速度的增加）。
- 暂停与继续的快捷键。
##符号$说明
function $(id){ //在文件base.js中
return document.getElementById(id);
}
##代码
<!DOCTYPE html>
<html>
<head>
<title>Snake</title>
<meta http-equiv="Content-Type" content="text/html;charset=utf-8">
<style type="text/css" >
body{background-color: #eee; font-family: 手札体-简;}
#page{width: 960px; height: 560px; margin: 30px auto; background-color: #fdf5e6;box-shadow: 3px 3px 3px rgba(0,0,0,0.2),10px 10px 20px rgba(0,0,0,0.2); border-radius: 5px;}
#page div{float: left;}
#left{width: 710px; height: 560px; }
table{margin: 20px 100px;background-color: #9cc;}
td{background-color: #cff;}
#right{width: 205px; height: 560px;}
#right div{float: none;}
#score{width: 200px; height: 190px;;background-color: #ffffe0; border-radius: 10px;box-shadow: 3px 3px 3px rgba(0,0,0,0.2),5px 5px 10px rgba(0,0,0,0.2);margin-top: 20px;}
#rank{width: 200px; height: 190px; margin-top: 10px;background-color: #ffffe0;border-radius: 10px;box-shadow: 3px 3px 3px rgba(0,0,0,0.2),5px 5px 10px rgba(0,0,0,0.2);}
#right .tag{height:30px; width: 200px ;font-size: 40px;color: #9cf;font-weight: bolder; }
#score_num{height: 130px; width: 200px; text-align: center;color: #9cf; font-size: 100px;}
#rank_num{height: 130px; width: 200px; text-align: center;color: #9cf; font-size: 100px;}
#notice{width: 200px;color: #9cf; margin-top: 5px;box-shadow: 3px 3px 3px rgba(0,0,0,0.2),5px 5px 10px rgba(0,0,0,0.2);background-color: #ffffe0; border-radius: 5px;margin-top: 90px;}
</style>
<script type="text/javascript" src="base.js"></script>
<script type="text/javascript">
//全局变量
var max_scope = 30;//贪吃蛇的移动范围
var unit = 13;//每一个单元格的大小
var speed = 300;//贪吃蛇移动速度
var direction = 'left';//贪吃蛇移动方向
var snake_body = null;
var interval = null;//计时器
var food = null;
var score = 0;//分数（每吃一次，分数加一）
var rank = 1;//随着分数的增加，等级逐渐增加，速度逐渐增加
//初始化游戏，使用表格做贪吃蛇移动的范围
function initGame(){
snake_body = new Array();
for(i = 0 ; i < max_scope; i++)
{
var row = document.createElement("tr");
for( j = 0 ; j < max_scope; j++)
{
var cell = document.createElement("td");
cell.id = i + "-" + j;
cell.width = unit;
cell.height = unit;
row.appendChild(cell);
}
$("tbody").appendChild(row);
}
initSnake();
snakeInterval();
initFood();
}
//贪吃蛇身体初始化（随机生成）
function initSnake(){
var x = parseInt(Math.random()*(max_scope-2));
var y = parseInt(Math.random()*(max_scope-2));
var now_position = x + "-" + y;
snake_body.push(now_position);
setCellState(now_position);
}
// 贪吃蛇身体染色
function setCellState(id){
$(id).style.background = "#000";
}
// 食物染色
function setFootState(id){
$(id).style.background = "#b10000";
}
// 贪吃蛇尾巴离开位置染色
function setCellStateBack(id){
$(id).style.background = "";
}
// 获取贪吃蛇坐标
function getSnakePos(i){
switch(i){
case 'x':
return snake_body[0].split('-')[0];
case 'y':
return snake_body[0].split('-')[1];
}
}
// 计时器
function snakeInterval(){
interval = window.setInterval('snakeMove()',speed);
}
// 初始化计时器
function resetSnakeInterval(){
window.clearInterval(interval);
interval = window.setInterval('snakeMove()',speed);
}
// 设置蛇的移动与移动过程中发生的事件
function snakeMove(){
foodx = food.split('-')[0];
foody = food.split('-')[1];
switch(direction){
case 'left':
_x = getSnakePos('x');
_y = parseInt(getSnakePos('y')) -1;
break;
case 'right':
_x = getSnakePos('x');
_y = parseInt(getSnakePos('y')) +1;
break;
case 'up':
_x = parseInt(getSnakePos('x')) -1;
_y = getSnakePos('y');
break;
case 'down':
_x = parseInt(getSnakePos('x')) +1;
_y = getSnakePos('y');
break;
default:
_x = getSnakePos('x');
_y = parseInt(getSnakePos('y')) -1;
break;
}
//撞到墙游戏结束
if (_x < 0 || _x >= max_scope|| _y < 0 || _y >= max_scope){
alert("Game Over! Stupid!");
window.clearInterval(interval);
}
//撞到自己游戏结束
else if (eatItself(_x, _y))
{
alert("Game Over! Stupid!");
window.clearInterval(interval);
}
//蛇吃到食物与吃到食物以后加一分，并设置相应的等级
else if (foodx == _x && foody == _y)
{
snake_body.unshift(foodx + '-' + foody);
setCellState(snake_body[0]);
initFood();
score+=1;
$('score_num').innerText = score;
if (score == 3) {
speed = 250;
resetSnakeInterval();
rank = 2;
}
if (score == 6) {
speed = 200;
resetSnakeInterval();
rank = 3;
}
if (score == 10) {
speed = 150;
resetSnakeInterval();
rank = 4;
}
if (score == 20) {
speed = 100;
resetSnakeInterval();
rank = 5;
}
if (score == 30) {
speed = 70;
resetSnakeInterval();
rank = 6;
}
//将等级写到层中
$('rank_num').innerText = rank;
}
//普通的移动
else {
snake_body.unshift(_x + '-' + _y);
setCellState(snake_body[0]);
setCellStateBack(snake_body.pop());
}
}
// 判断贪吃蛇头碰到身体的函数
function eatItself( x,y){
var nowpos = x + '-' + y;
for (i = 1 ; i < snake_body.length; i++){
if (nowpos == snake_body[i])
return true;
}
}
// 设置蛇的移动方向以及键盘控制暂停与继续
function setDirction(){
// alert(event.keyCode);
if (event.keyCode == 81) window.clearInterval(interval);
if (event.keyCode == 82) interval = window.setInterval('snakeMove()',speed);
switch (event.keyCode){
case 37:
if (direction != "right")
direction = "left";
break;
case 38:
if (direction != "down")
direction = "up";
break;
case 39:
if (direction != "left")
direction = "right";
break;
case 40:
if (direction != "up")
direction = "down";
break;
}
}
// 初始化食物
function initFood(){
var temp = new Array();
for (i = 0 ; i < max_scope ; i++){
for (j = 0 ; j < max_scope; j++){
temp.push(i + '-' + j);
}
}
var addFoodString = temp.join(',')+',';
for(k = 0 ; k <snake_body.length; k++){
addFoodString = addFoodString.replace(snake_body[k]+',',"")
}
var food_array = addFoodString.split(',');
food = food_array[parseInt(Math.random()*(food_array.length - 1))]
setFootState(food);
// $('display').innerText = addFoodString;
}
// function pause(){
// if (event.keyCode == 81)
// window.clearInterval(interval);
// }
</script>
</head>
<body onload="initGame()" onkeydown="setDirction()" >
<div id = "page">
<div id = "left">
<table>
<tbody id = "tbody">
</tbody>
</table>
</div>
<div id = "right">
<div id = "score">
<div class = "tag">Score</div>
<div id = "score_num">0</div>
</div>
<div id = "rank">
<div class = "tag">Rank</div>
<div id = "rank_num">1</div>
</div>
<div id = "notice">NOTICE：按'Q'暂停，'E'继续</div>
</div>
</div>
<!-- <div id = "display"> </div> -->
</body>
</html>
以下是效果图：
