以下内容为学习记录，可以参考 MDN 原文。
环境
- vscode 1.46
- Microsoft Edge 83
示例
以下内容为了解和熟悉 JavaScript，不需要理解，能够复制粘贴并正确运行即可。
新建网页模板
在 vscode 中新建一个 index.html 文件，然后输入以下内容。
<!DOCTYPE html>
<html>
<head>
<meta charset="utf-8">
<title>猜数字游戏</title>
<style>
html {
font-family: sans-serif;
}
body {
50%;
max- 800px;
min- 480px;
margin: 0 auto;
}
.lastResult {
color: white;
padding: 3px;
}
</style>
</head>
<body>
<h1>猜数字游戏</h1>
<p>我刚才随机选定了一个100以内的自然数。看你能否在 10 次以内猜中它。每次我都会告诉你所猜的结果是高了还是低了。</p>
<div class="form">
<label for="guessField">请猜数: </label>
<input type="text" id="guessField" class="guessField">
<input type="submit" value="确定" class="guessSubmit">
</div>
<div class="resultParas">
<p class="guesses"></p>
<p class="lastResult"></p>
<p class="lowOrHi"></p>
</div>
<script>
// 开始编写 JavaScript 代码
</script>
</body>
</html>
定义变量
首先将需要使用的变量都定义出来。
let randomNumber = Math.floor(Math.random() * 100) + 1;
const guesses = document.querySelector('.guesses');
const lastResult = document.querySelector('.lastResult');
const lowOrHi = document.querySelector('.lowOrHi');
const guessSubmit = document.querySelector('.guessSubmit');
const guessField = document.querySelector('.guessField');
let guessCount = 1;
let resetButton;
定义猜数字主逻辑
function checkGuess() {
let userGuess = Number(guessField.value);
if (guessCount === 1) {
guesses.textContent = '上次猜的数：';
}
guesses.textContent += userGuess + ' ';
if (userGuess === randomNumber) {
lastResult.textContent = '恭喜你！猜对了';
lastResult.style.backgroundColor = 'green';
lowOrHi.textContent = '';
setGameOver();
} else if (guessCount === 10) {
lastResult.textContent = '!!!GAME OVER!!!';
setGameOver();
} else {
lastResult.textContent = '你猜错了！';
lastResult.style.backgroundColor = 'red';
if(userGuess < randomNumber) {
lowOrHi.textContent = '你猜低了！';
} else if(userGuess > randomNumber) {
lowOrHi.textContent = '你猜高了';
}
}
guessCount++;
guessField.value = '';
guessField.focus();
}
结束游戏
function setGameOver() {
guessField.disabled = true;
guessSubmit.disabled = true;
resetButton = document.createElement('button');
resetButton.textContent = '开始新游戏';
document.body.appendChild(resetButton);
resetButton.addEventListener('click', resetGame);
}
重置游戏
function resetGame() {
guessCount = 1;
const resetParas = document.querySelectorAll('.resultParas p');
for (let i = 0 ; i < resetParas.length; i++) {
resetParas[i].textContent = '';
}
resetButton.parentNode.removeChild(resetButton);
guessField.disabled = false;
guessSubmit.disabled = false;
guessField.value = '';
guessField.focus();
lastResult.style.backgroundColor = 'white';
randomNumber = Math.floor(Math.random() * 100) + 1;
}
浏览器打开
用浏览器打开刚刚编写的程序，试试游戏是否能够正常运行。
附录
源码
<!DOCTYPE html>
<html>
<head>
<meta charset="utf-8">
<title>猜数字游戏</title>
<style>
html {
font-family: sans-serif;
}
body {
50%;
max- 800px;
min- 480px;
margin: 0 auto;
}
.lastResult {
color: white;
padding: 3px;
}
</style>
</head>
<body>
<h1>猜数字游戏</h1>
<p>我刚才随机选定了一个100以内的自然数。看你能否在 10 次以内猜中它。每次我都会告诉你所猜的结果是高了还是低了。</p>
<div class="form">
<label for="guessField">请猜数: </label>
<input type="text" id="guessField" class="guessField">
<input type="submit" value="确定" class="guessSubmit">
</div>
<div class="resultParas">
<p class="guesses"></p>
<p class="lastResult"></p>
<p class="lowOrHi"></p>
</div>
<script>
let randomNumber = Math.floor(Math.random() * 100) + 1;
const guesses = document.querySelector('.guesses');
const lastResult = document.querySelector('.lastResult');
const lowOrHi = document.querySelector('.lowOrHi');
const guessSubmit = document.querySelector('.guessSubmit');
const guessField = document.querySelector('.guessField');
let guessCount = 1;
let resetButton;
function checkGuess() {
let userGuess = Number(guessField.value);
if (guessCount === 1) {
guesses.textContent = '上次猜的数：';
}
guesses.textContent += userGuess + ' ';
if (userGuess === randomNumber) {
lastResult.textContent = '恭喜你！猜对了';
lastResult.style.backgroundColor = 'green';
lowOrHi.textContent = '';
setGameOver();
} else if (guessCount === 10) {
lastResult.textContent = '!!!GAME OVER!!!';
setGameOver();
} else {
lastResult.textContent = '你猜错了！';
lastResult.style.backgroundColor = 'red';
if (userGuess < randomNumber) {
lowOrHi.textContent = '你猜低了！';
} else if (userGuess > randomNumber) {
lowOrHi.textContent = '你猜高了';
}
}
guessCount++;
guessField.value = '';
guessField.focus();
}
guessSubmit.addEventListener('click', checkGuess);
function setGameOver() {
guessField.disabled = true;
guessSubmit.disabled = true;
resetButton = document.createElement('button');
resetButton.textContent = '开始新游戏';
document.body.appendChild(resetButton);
resetButton.addEventListener('click', resetGame);
}
function resetGame() {
guessCount = 1;
const resetParas = document.querySelectorAll('.resultParas p');
for (let i = 0; i < resetParas.length; i++) {
resetParas[i].textContent = '';
}
resetButton.parentNode.removeChild(resetButton);
guessField.disabled = false;
guessSubmit.disabled = false;
guessField.value = '';
guessField.focus();
lastResult.style.backgroundColor = 'white';
randomNumber = Math.floor(Math.random() * 100) + 1;
}
</script>
</body>
</html>