[转载代码] JS版贪吃蛇

function Snake(canvas){
	this.canvas = canvas;
	this.length = 0;
	this.direction = 'down';
	this.body = [],
	this.head = function(){
		return this.length == 0 ? null : this.body[0];
	};
	this.isAlive = true;
	this.onDie = null;
	this.onEat = null;
	this.speed = 300;
	this.auto = null;
	this.turned = false;
	this.turn = function(d){
		if(this.turned){
			return;
		}else{
			switch(d){
				case 'left':
				case 'right':
					if(this.direction == 'left' || this.direction == 'right'){
						return;
					}
					break;
				case 'up':
				case 'down':
					if(this.direction == 'up' || this.direction == 'down'){
						return;
					}
					break;
			}
			this.direction = d;
			this.turned = true;
		}
	}
	this.turnLeft = function(){this.turn('left');};
	this.turnRight = function(){this.turn('right')};
	this.turnUp = function(){this.turn('up')};
	this.turnDown = function(){this.turn('down')};
	this.moveTo = function(x, y){
		this.canvas.clsCanvas(this);
		this.body.pop();
		this.length--;
		this.grow(x, y);
		this.canvas.drawSnake(this);
		this.turned = false;
	};
	this.grow = function(bX, bY){
		var head = {
			x : bX,
			y : bY
		};
		this.body.unshift(head);
		this.length++;
	};
	this.stepWalk = function(){
		if(!this.isAlive){return;}
		if(!this.head()){
			throw new Error('this snake is not initialized');
		}
		var nextBlock, head = this.head();
		var nX = head.x, nY = head.y;
		switch(this.direction){
			case 'down':
				nY = head.y + 1;
				break;
			case 'up':
				nY = head.y - 1;
				break;
			case 'left':
				nX = head.x - 1;
				break;
			case 'right':
				nX = head.x + 1;
				break;
		}
		if(nX < 1 || nY < 1 || nX > canvas.width || nY > canvas.height || this.contains(nX, nY)){
			this.isAlive = false;
			if(this.onDie){this.onDie();}
		}else{
			nextBlock = this.canvas.getBlock(nX, nY);
			if(this.canvas.isFoodBlock(nextBlock)){
				nextBlock.setAttribute('food','');	// the food has been eaten
				this.grow(nX, nY);
				if(this.onEat){this.onEat();}
				var t = this;
				setTimeout(function(){t.stepWalk();},80 );
			}else{
				this.moveTo(nX, nY);
			}
		}
	};
	this.autoWalk = function(){
		var snake = this;
		this.auto = setInterval(function(){
								if(snake.isAlive){
									snake.stepWalk();
								}else{
									clearInterval(snake.auto);
								}
							}, this.speed );
	};
	this.contains = function(x,y){
			var len = this.length, snakeBody = this.body, b;
			for(var i=0;i<len;i++){
				b = snakeBody[i];
				if(b.x == x && b.y == y){
					return true;
				}
			}
			return false;
	};
	this.init = function(length){
		if(length<this.canvas.height){
			for(var i=0; i<length;i++){
				this.grow(1, i+1);
			}
		};
		this.canvas.drawSnake(this);
		this.canvas.createFood();
	},
	this.pause = function(){
		if(this.auto){
			clearInterval(this.auto);
			this.auto = null;
		}
	};	
}
function SnakeCanvas(div){
	this.target = div;
	this.createView();
}
SnakeCanvas.prototype = {
	width: 20,
	height: 16,
	currentSnake : null,
	createView : function(){
		var i = 0, span;
		addClass(this.target, 'target');
		
		while(i < 320){
			span = document.createElement('span');
			span.id = 'span_' + (++i);
			addClass(span, 'blocks');
			this.target.appendChild( span );
		}
	},
	getBlock : function(x, y){
		return document.getElementById('span_' + (y ? ((y-1) * this.width + x) : (x+1)));
	},
	activateBlock : function(block){
		block.setAttribute('act', 'true');
		addClass(block, 'snake-body');
	},
	inActivateBlock: function(block){
		block.setAttribute('act', '');
		removeClass(block, 'snake-body');
	},
	switchBlock: function(block){
		var active = block.getAttribute('act');
		if(active){
			this.inActivateBlock(block);
		}else{
			this.activateBlock(block);
		}
	},
	isFoodBlock: function(block){
		return !!(block.getAttribute('food'));
	},
	createFood : function(){
		var posX = 0, posY = 0, done = false, block;
		while( !done){
			posX = Math.floor(Math.random() * (this.width + 1));
			posY = Math.floor(Math.random() * (this.height + 1));
			if(posX == 0){ posX = 1;} if(posY == 0){ posY = 1;}
			block = this.getBlock(posX, posY);
			if(!this.currentSnake || (!this.currentSnake.contains(posX, posY))){
				block.setAttribute('food', 'true');
				this.switchBlock(block);
				done = true;
			}
		}
	},
	clsCanvas : function(snake){
		var snakeBlock, i = 0;
		if(snake){
			for(;i<snake.length;i++){
				snakeBlock = snake.body[i];
				this.inActivateBlock(this.getBlock(snakeBlock.x, snakeBlock.y));
			}
		}else{
			while(i< this.width * this.height){
				this.inActivateBlock(this.getBlock(i));
			}
		}
	},
	drawSnake : function(snake){
		var snakeBlock;
		for(var i=0;i<snake.length;i++){
			snakeBlock = snake.body[i];
			this.activateBlock(this.getBlock(snakeBlock.x, snakeBlock.y));
		}
		this.currentSnake = snake;
	}
};
//---------------------------//

function trim(text){
	var	rnotwhite = /\S/,
	// Used for trimming whitespace
	trimLeft = /^\s+/,
	trimRight = /\s+$/;	

	// IE doesn't match non-breaking spaces with \s
	if ( rnotwhite.test( "\xA0" ) ) {
		trimLeft = /^[\s\xA0]+/;
		trimRight = /[\s\xA0]+$/;
	}
	
	return text.toString().replace( trimLeft, "" ).replace( trimRight, "" );
}

function addClass(elem, className){
	var setClass;
	if ( elem.nodeType === 1 ) {
		if ( !elem.className ) {
			elem.className = className;

		} else {
			setClass = " " + elem.className + " ";
			if ( !~setClass.indexOf( " " + className + " " ) ) {
				setClass += className + " ";
			}
			elem.className = trim(setClass);
		}
	}
}

function removeClass(elem, value){
	var className;
	if ( elem.nodeType === 1 && elem.className ) {
		if ( value ) {
			className = (" " + elem.className + " ").replace( /[\n\t\r]/g, " " );
			className = className.replace(" " + value + " ", " ");
			elem.className = trim( className );
		} else {
			elem.className = "";
		}
	}
}
 function keyDown(e){
	if(!snake || !snake.isAlive) {
		return;
	}
	e=e||window.event;
	var keyCode = e.keyCode||e.which||e.charCode;
	switch(keyCode){
		case 37://左
			snake.turnLeft();
			break;
		case 38://上
			snake.turnUp();
			break;
		case 39://右
			snake.turnRight();
			break;
		case 40://下
			snake.turnDown();
			break;
		case 80://p 暂停or开始
		case 229:
			if(snake.auto){
				snake.pause();
			}else{
				snake.autoWalk();
			}
			break;
	}
}
if(document.attachEvent){
	document.attachEvent('onkeydown', keyDown);
}else if(document.addEventListener){
	document.addEventListener('keydown', keyDown, false);
}
</SCRIPT>

<STYLE>DIV {
	MARGIN: 20px auto
}
.target {
	BORDER-BOTTOM: black 1px solid; BORDER-LEFT: black 1px solid; WIDTH: 400px; DISPLAY: block; HEIGHT: 320px; OVERFLOW: hidden; BORDER-TOP: black 1px solid; BORDER-RIGHT: black 1px solid
}
.blocks {
	BORDER-BOTTOM: #ddd 1px dotted; BORDER-LEFT: #ddd 1px dotted; WIDTH: 18px; DISPLAY: block; FLOAT: left; HEIGHT: 18px; BORDER-TOP: #ddd 1px dotted; BORDER-RIGHT: #ddd 1px dotted
}
.snake-body {
	BORDER-BOTTOM-STYLE: solid; BORDER-RIGHT-STYLE: solid; BACKGROUND-COLOR: #111; BORDER-TOP-STYLE: solid; BORDER-LEFT-STYLE: solid
}
</STYLE>

<META name=GENERATOR content="MSHTML 8.00.7601.17537"></HEAD>
<BODY>
<H1>Snake</H1>
<DIV id=t></DIV>
<DIV>您的得分是：<SPAN id=s>0</SPAN></DIV>
<DIV>操作提示：按上下左右键操作，按 P 键暂停或继续 </DIV>
<SCRIPT>
var canvas = new SnakeCanvas( document.getElementById('t') );
var snake = new Snake( canvas );
var score = 0, initSpeed = snake.speed;
snake.onDie = function(){
	alert('game over');
};
snake.onEat = function(){
	snake.canvas.createFood();
	score++;
	var speed = initSpeed;
	if(score % 5 == 0){
		speed -= 10;
	}
	if(speed < 100){
		speed = 100;
	}
	snake.speed = speed;
	document.getElementById('s').innerHTML = score * 100 ;
};
snake.init(3);
snake.autoWalk();
// snake.pause();
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