借助HTML5 Canvas API制作一个简单的猜字游戏_html5教程_前端技术

二话不说，先上效果图以及源代码~
借助HTML5 Canvas API制作一个简单的猜字游戏

HTML代码

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<!doctype html>
<html lang="en">
<head>
<meta charset="utf-8" />
<script type="text/javascript" src="chp1_guess_the_letter.js"></script>
<script type="text/javascript" src="modernizr.custom.99886.js"></script>
</head>
<body>
<canvas id="canvas_guess_the_letter" width="500" height="300">
你的浏览器不支持HTML5 Canvas
</canvas>
<form>
<input type="button" id="createImageData" value="Export Canvas Image" />;
</form>
</body>
</html>

JS代码

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/**
* @author Rafael
*/
window.addEventListener("load", eventWindowLoaded, false);
var Debugger = function() {
};
Debugger.log = function(message) {
try {
console.log(message);
} catch(exception) {
return;
}
}
function eventWindowLoaded() {
canvasApp();
}
function canvasSupport() {
return Modernizr.canvas;
}
function canvasApp() {
var guesses = 0;
var message = "Guess The Letter From a(lower) to z(higher)";
var letters = ["a","b","c","d","e","f","g","h","i","j","k","l",
"m","n","o","p","q","r","s","t","u","v","w","x","y","z"];
var today = new Date();
var letterToGuess = "";
var higherOrLower = "";
var letterGuessed = [];
var gameOver = false;
if(!canvasSupport()) {
return;
}
var theCanvas = document.getElementById("canvas_guess_the_letter");
var context = theCanvas.getContext("2d");
initGame();
function initGame() {
var letterIndex = Math.floor(Math.random() * letters.length);
letterToGuess = letters[letterIndex];
guesses = 0;
lettersGuessed = [];
gameOver = false;
window.addEventListener("keyup", eventKeyPressed, true);
var formElement = document.getElementById("createImageData");
formElement.addEventListener('click', createImageDataPressed, false);
drawScreen();
}
function eventKeyPressed(e) {
if(!gameOver) {
var letterPressed = String.fromCharCode(e.keyCode);
letterPressed = letterPressed.toLowerCase();
guesses++;
letterGuessed.push(letterPressed);
if(letterPressed == letterToGuess) {
gameOver = true;
} else {
letterIndex = letters.indexOf(letterToGuess);
guessIndex = letters.indexOf(letterPressed);
if(guessIndex < 0) {
higherOrLower = "请输入正确的字符";
} else if(guessIndex < letterIndex) {
higherOrLower = "小了";
} else {
higherOrLower = "大了";
}
}
drawScreen();
}
}
function drawScreen() {
//背景
context.fillStyle = "#ffffaa";
context.fillRect(0, 0, 500, 300);
//箱子
context.strokeStyle = "#000000";
context.strokeRect(5, 5, 490, 290);
context.textBaseLine = "top";
//日期
context.fillStyle = "#000000";
context.font = "10px _sans";
context.fillText(today, 150, 20);
//消息
context.fillStyle = "#FF0000";
context.font = "14px _sans";
context.fillText(message, 125, 40);
//猜测次数
context.fillStyle = "#109900";
context.font = "16px _sans";
context.fillText("猜测次数： "+guesses, 215, 60);
//大还是小
context.fillStyle = "#000000";
context.font = "16px _sans";
context.fillText("大还是小： "+higherOrLower, 150, 135);
//已经猜测的字符
context.fillStyle = "#FF0000";
context.font = "16px _sans";
context.fillText("已经猜测的字符： "+letterGuessed.toString(), 10, 260);
if(gameOver) {
context.fillStyle = "#FF0000";
context.font = "40px _sans";
context.fillText("你猜中了", 150, 180);
}
}
function createImageDataPressed(e) {
window.open(theCanvas.toDataURL(), "canvasImage","left=0, top=0, width="+theCanvas.width+", height="+theCanvas.height+", toolbar=0, resizable=0");
}
}

从游戏名称可以看出，该游戏是猜字游戏。每局系统都会自动生成一个字母，玩家会按键盘来猜测该字母是哪一个。

例如生成的是s，玩家按了h，则游戏就会提示《小了》，因为英文字母当中h的索引比s的索引更靠前。

案例当中涉及的变量。

guesses：猜测次数
message：文字提示，指导用户如何玩该游戏
letters：文字数组，存放我们要猜测的文字的集合。这个例子用的是a到z
today：今天的日期
letterToGuess：要猜测的文字
higherOrLower：是《大了》还是《小了》
letterGuessed：已经猜测过得文字
gameOver：游戏是否结束，是布尔变量，开始的时候是false，猜对后设为true

变量的声明

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