一、游戏规则
21点游戏的规则有很多种，我在写这个21点游戏的时候，选取了一种规则，描述如下：
1、游戏共有两名玩家，玩家1（庄家）和玩家2，在我编写的这个21点中，玩家1是电脑，玩家2是你，电脑坐庄。
2、一开始，给你和庄家各发两张牌，你可以看到你的两张牌，庄家的牌一张是明牌，一张是暗牌（暗牌是扣过来的牌，你不知道具体点数是多少）。
3、你和庄家的牌都是从一副牌里发出来的，共计52张（不要大小Joker）。
4、A可以当做1点和11点用，J、Q、K当做10点用，其他牌按面值计算点数。
5、发牌后，你可以选择要或不要牌，选择要牌后，如果你的点数大于21点，你就输了，否则你还可以选择要或不要牌，如果你选择不要牌，则轮到庄家要牌。
6、轮到庄家时，如果庄家的点数小于17点，则庄家必须要牌，当庄家点数大于或等于17时，庄家有权继续选择要或不要。如果庄家点数大于21点，则判定庄家输。
7、如果你和庄家都不要了，且双方都没有爆掉，则双方摊牌，计算双方点数，以点数大者胜，若双方点数一致则为平局。
二、目录结构
游戏的目录结构如下：
1、resource目录下，存储了游戏需要使用的图片。
2、bgm.ogg是游戏的背景音乐（我把QQ斗地主的背景音乐放进来了╮(╯▽╰)╭）
3、black_jack.html是一个网页，使用浏览器打开它就可以开始进行游戏了
4、black_jack.js存储了JavaScript代码
resource目录下的图片，包括纸牌图案、玩家头像等内容：
三、页面代码
black_jack.html页面代码如下：
<html>
<head>
<title>JS学习 - 21点 (black jack)</title>
<meta http-equiv="Content-Type" content="text/html;charset=gb2312"/>
</head>
<style type="text/css">
table th
{
text-align: center;
text-decoration: none;
font-weight: normal;
padding: 3px 6px 3px 6px;
width:200px;
}
table td
{
vertical-align: center;
text-align: center;
padding: 3px 6px 3px 6px;
margin: 0px;
}
</style>
<body>
<table width="100%">
<tr>
<td>
<div align="left">
21点游戏 (Black Jack)
</div>
</td>
<td>
<div align="right">
<audio width="300" height="10" controls autoplay="true" loop="true">
<source src="bgm.ogg" type="video/ogg"/>
</audio>
</div>
</td>
</tr>
</table>
<hr>
<table id="tableboard">
<tr>
<td id="player1"><img src="resource\computer.png" /></td>
<td/><td/><td/><td/><td/><td/><td/><td/><td/><td/><td/><td/><td/>
</tr>
<tr>
<td id="player2"><img src="resource\player.jpg" /></td>
<td/><td/><td/><td/><td/><td/><td/><td/><td/><td/><td/><td/><td/>
</tr>
</table>
<hr>
<table>
<tr>
<td>
<div id="score"></div>
</td>
<td>
<div id="bulletin">请做出选择 (Please make a choice.)</div>
</td>
</tr>
</table>
<hr>
<input type="button" id="hit" value="加一张牌 (HIT)" onclick="hit();" />
<input type="button" id="stand" value="我不要了 (STAND)" onclick="stand();" />
<!--<input type="button" id="restart" value="再玩一局 (FIGHT AGAIN)" onclick="location.reload();" />-->
<input type="button" id="restart" value="再玩一局 (FIGHT AGAIN)" onclick="restart();" />
<script src="black_jack.js"></script>
</body>
</html>black_jack.js页面代码如下：
//Firefox44.0，如果再来一局功能用location.reload()实现，则必须带上这两句话
//document.getElementById("hit").disabled = false;
//document.getElementById("stand").disabled = false;
var counter = 0; //发牌次数
var winner = ""; //胜利者 player1 - 电脑/player2 - 玩家
var hasStood = false; //标记玩家是否已经不要牌
//所有的牌
var cards = [
"club01", "club02", "club03", "club04", "club05", "club06", "club07",
"club08", "club09", "club10", "club11", "club12", "club13", "diamond01",
"diamond02", "diamond03", "diamond04", "diamond05", "diamond06", "diamond07",
"diamond08", "diamond09", "diamond10", "diamond11", "diamond12", "diamond13",
"heart01", "heart02", "heart03", "heart04", "heart05", "heart06", "heart07",
"heart08", "heart09", "heart10", "heart11", "heart12", "heart13",
"spade01", "spade02", "spade03", "spade04", "spade05", "spade06", "spade07",
"spade08", "spade09", "spade10", "spade11", "spade12", "spade13"];
//生成随机数
var getRand = function (begin, end) {
return Math.floor(Math.random() * (end - begin)) + begin;
}
//洗牌
var rand, tmp;
for (var i = 0; i < 1000; i++) {
rand = getRand(1, 52);
tmp = cards[0];
cards[0] = cards[rand];
cards[rand] = tmp;
}
//玩家手牌
var cards1 = [getNewCard(), getNewCard()];
var cards2 = [getNewCard(), getNewCard()];
var table = document.getElementById("tableboard");
table.rows[0].cells[1].innerHTML = "<img src=\"resource\\cardback.png\" />";
table.rows[0].cells[2].innerHTML = "<img src=\"resource\\" + cards1[1] + ".jpg\" />";
table.rows[1].cells[1].innerHTML = "<img src=\"resource\\" + cards2[0] + ".jpg\" />";
table.rows[1].cells[2].innerHTML = "<img src=\"resource\\" + cards2[1] + ".jpg\" />";
showScore();
//玩家再要一张牌
function hit() {
getNewCard("player2");
if(checkIfBust("player2")) {
document.getElementById("bulletin").innerHTML = "你爆了 (You BUST!)";
document.getElementById("hit").disabled = true;
document.getElementById("stand").disabled = true;
winner = "player1";
}
showScore();
}
//玩家选择不要了
function stand() {
hasStood = true;
document.getElementById("hit").disabled = true;
document.getElementById("stand").disabled = true;
table.rows[0].cells[1].innerHTML = "<img src=\"resource\\" + cards1[0] + ".jpg\" />";
//电脑开始要牌
while (calcResult("player1") < 17) {
getNewCard("player1");
if(checkIfBust("player1")) {
document.getElementById("bulletin").innerHTML = "电脑爆了 (Computer BUST!)";
document.getElementById("hit").disabled = true;
document.getElementById("stand").disabled = true;
winner = "player2";
}
}
//如两名玩家都未爆掉，则以分数高者为胜
if (winner == "") {
var result1 = calcResult("player1");
var result2 = calcResult("player2");
if (result1 == result2) {
document.getElementById("bulletin").innerHTML = "平局 (PUSH!)";
} else if (result1 > result2) {
document.getElementById("bulletin").innerHTML = "你输了 (You LOSE)";
} else if (result1 < result2) {
document.getElementById("bulletin").innerHTML = "你赢了 (You WIN!)";
}
}
showScore();
}
//获取一张新牌
function getNewCard(player) {
var card = cards[counter++];
if (player == "player1") {
var len = cards1.length;
cards1[len] = card;
table.rows[0].cells[len + 1].innerHTML =
"<img src=\"resource\\" + cards1[len] + ".jpg\" />";
} else if (player == "player2") {
var len = cards2.length;
cards2[len] = card;
table.rows[1].cells[len + 1].innerHTML =
"<img src=\"resource\\" + cards2[len] + ".jpg\" />";
}
return card;
}
//判断当前情况是否爆掉
function checkIfBust(player) {
var result = 0;
if (player == "player1") {
for (var i = 0; i < cards1.length; i++) {
//parseInt一定要指定10进制，否则IE8下报错
var c = parseInt(cards1[i].substr(cards1[i].length - 2), "10");
if (c > 10) {
c = 10;
}
result += c;
}
if (result > 21) {
return true;
} else {
return false;
}
} else if (player == "player2") {
for (var i = 0; i < cards2.length; i++) {
var c = parseInt(cards2[i].substr(cards2[i].length - 2), "10");
if (c > 10) {
c = 10;
}
result += c;
}
if (result > 21) {
return true;
} else {
return false;
}
}
}
//计算一名玩家的得分分数
function calcResult(player) {
var result = 0;
var countOfA = 0;
if (player == "player1") {
for (var i = 0; i < cards1.length; i++) {
var c = parseInt(cards1[i].substr(cards1[i].length - 2), "10");
if (c > 10) {
c = 10;
} else if (c == 1) {
countOfA++;
}
result += c;
}
for (var i = 0; i < countOfA; i++) {
if (result + 10 <= 21) {
result += 10;
} else {
break;
}
}
} else {
for (var i = 0; i < cards2.length; i++) {
var c = parseInt(cards2[i].substr(cards2[i].length - 2), "10");
if (c > 10) {
c = 10;
} else if (c == 1) {
countOfA++;
}
result += c;
}
for (var i = 0; i < countOfA; i++) {
if (result + 10 <= 21) {
result += 10;
} else {
break;
}
}
}
return result;
}
function showScore() {
var result1 = calcResult("player1");
var result2 = calcResult("player2");
document.getElementById("score").innerHTML =
"[Computer : You = " + (hasStood == true ? result1 : "?") + " : " + result2 + "]";
}
function restart() {
document.getElementById("hit").disabled = false;
document.getElementById("stand").disabled = false;
counter = 0; //发牌次数
winner = ""; //胜利者 player1 - 电脑/player2 - 玩家
hasStood = false; //标记玩家是否已经不要牌
cards = [
"club01", "club02", "club03", "club04", "club05", "club06", "club07",
"club08", "club09", "club10", "club11", "club12", "club13", "diamond01",
"diamond02", "diamond03", "diamond04", "diamond05", "diamond06", "diamond07",
"diamond08", "diamond09", "diamond10", "diamond11", "diamond12", "diamond13",
"heart01", "heart02", "heart03", "heart04", "heart05", "heart06", "heart07",
"heart08", "heart09", "heart10", "heart11", "heart12", "heart13",
"spade01", "spade02", "spade03", "spade04", "spade05", "spade06", "spade07",
"spade08", "spade09", "spade10", "spade11", "spade12", "spade13"];
//洗牌
for (var i = 0; i < 1000; i++) {
rand = getRand(1, 52);
tmp = cards[0];
cards[0] = cards[rand];
cards[rand] = tmp;
}
//玩家手牌
cards1 = [getNewCard(), getNewCard()];
cards2 = [getNewCard(), getNewCard()];
table.rows[0].cells[1].innerHTML = "<img src=\"resource\\cardback.png\" />";
table.rows[0].cells[2].innerHTML = "<img src=\"resource\\" + cards1[1] + ".jpg\" />";
table.rows[1].cells[1].innerHTML = "<img src=\"resource\\" + cards2[0] + ".jpg\" />";
table.rows[1].cells[2].innerHTML = "<img src=\"resource\\" + cards2[1] + ".jpg\" />";
//清空牌桌
for (var i = 3; i < table.rows[0].cells.length; i++) {
table.rows[0].cells[i].innerHTML = "";
table.rows[1].cells[i].innerHTML = "";
}
showScore();
document.getElementById("bulletin").innerHTML = "请做出选择 (Please make a choice.)";
}
/*
//播放背景音乐 - Chrome46.0.2490.80m有效，Firefox44.0无效
var mp3snd = "./bgm.ogg";
var bkcolor = "000000";
if (navigator.userAgent.toLowerCase().indexOf("msie") != -1) {
document.write('<bgsound src="' + mp3snd + '" loop="-1">');
} else if (navigator.userAgent.toLowerCase().indexOf("firefox") != -1) {
document.write('<object data="' + mp3snd + '" type="application/x-mplayer2" width="0" height="0">');
document.write('<param name="filename" value="' + mp3snd + '">');
document.write('<param name="autostart" value="1">');
document.write('<param name="playcount" value="infinite">');
document.write('</object>');
} else {
document.write('<audio src="' + mp3snd + '" autoplay="autoplay" loop="loop">');
document.write('<object data="' + mp3snd + '" type="application/x-mplayer2" width="0" height="0">');
document.write('<param name="filename" value="' + mp3snd + '">');
document.write('<param name="autostart" value="1">');
document.write('<embed height="2" width="2" src="' + mp3snd + '" pluginspage="http://www.apple.com/quicktime/download/" type="video/quicktime" controller="false" controls="false" autoplay="true" autostart="true" loop="true" bgcolor="#' + bkcolor + '"><br>');
document.write('</embed></object>');
document.write('</audio>');
}*/
四、效果演示
使用Firefox浏览器（版本号44.0）打开black_jack.html后，效果如下图所示：
游戏代码可以从这个链接下载到：http://pan.baidu.com/s/1c1v2MQk
五、几点感受
1、我在IE8（版本8.0.7601.17514）、Chrome（版本46.0.2490.80 m）、Firefox（44.0）三个浏览器上测试了效果，除IE8中无法播放音乐外，其他功能都是正常的。
2、浏览器兼容性问题确实是个令人头疼的问题，就以parseInt函数来说，传入参数为"08"时，IE8返回0，Chrome和Firefox返回8。后来查了下才知道，原来IE8把字符串第一个字符为0的数字自动解析为八进制数了，需要在parseInt的第二个参数中强制指定使用十进制规则转换，才能让三个浏览器返回同样的结果。
3、说句题外话，这个游戏里，电脑赢的概率比你大，毕竟赌博游戏永远是庄家占便宜╭(╯^╰)╮。
END
来源：oschina
链接：https://my.oschina.net/u/1425762/blog/613176