开始学习 HTML

<p>My cat is very grumpy</p>

<h2>实时输出</h2>
<div class="output" style="min-height: 50px;"></div>

<h2>可编辑代码</h2>
<p class="a11y-label">
  按 ESC 退出编辑区域，按 Tab 可插入制表符 <code>'\t'</code>
</p>

<textarea id="code" class="playable-code" style="min-height: 100px;width: 95%">
  刀枪剑戟 斧钺钩叉
</textarea>

<div class="controls">
  <input id="reset" type="button" value="重置" />
  <input id="solution" type="button" value="显示答案" />
</div>

html {
  font-family: "Open Sans Light", Helvetica, Arial, sans-serif;
}

h2 {
  font-size: 16px;
}

.a11y-label {
  margin: 0;
  text-align: right;
  font-size: 0.7rem;
  width: 98%;
}

body {
  margin: 10px;
  background: #f5f9fa;
}

const textarea = document.getElementById("code");
const reset = document.getElementById("reset");
const solution = document.getElementById("solution");
const output = document.querySelector(".output");
const code = textarea.value;
let userEntry = textarea.value;

function updateCode() {
  output.innerHTML = textarea.value;
}

const htmlSolution = "<em>刀枪剑戟 斧钺钩叉</em>";
let solutionEntry = htmlSolution;

reset.addEventListener("click", () => {
  textarea.value = code;
  userEntry = textarea.value;
  solutionEntry = htmlSolution;
  solution.value = "显示答案";
  updateCode();
});

solution.addEventListener("click", () => {
  if (solution.value === "显示答案") {
    textarea.value = solutionEntry;
    solution.value = "隐藏答案";
  } else {
    textarea.value = userEntry;
    solution.value = "显示答案";
  }
  updateCode();
});

textarea.addEventListener("input", updateCode);
window.addEventListener("load", updateCode);

// stop tab key tabbing out of textarea and
// make it write a tab at the caret position instead
textarea.onkeydown = (e) => {
  if (e.keyCode === 9) {
    e.preventDefault();
    insertAtCaret("\t");
  }

  if (e.keyCode === 27) {
    textarea.blur();
  }
};

function insertAtCaret(text) {
  const scrollPos = textarea.scrollTop;
  let caretPos = textarea.selectionStart;

  const front = textarea.value.substring(0, caretPos);
  const back = textarea.value.substring(
    textarea.selectionEnd,
    textarea.value.length,
  );
  textarea.value = front + text + back;
  caretPos += text.length;
  textarea.selectionStart = caretPos;
  textarea.selectionEnd = caretPos;
  textarea.focus();
  textarea.scrollTop = scrollPos;
}

// Update the saved userCode every time the user updates the text area code

textarea.onkeyup = () => {
  // We only want to save the state when the user code is being shown,
  // not the solution, so that solution is not saved over the user code
  if (solution.value === "显示答案") {
    userEntry = textarea.value;
  } else {
    solutionEntry = textarea.value;
  }

  updateCode();
};

<p>My cat is <strong>very</strong> grumpy.</p>

<p>My cat is <strong>very grumpy.</p></strong>

<em>第一</em><em>第二</em><em>第三</em>

<p>第四</p>
<p>第五</p>
<p>第六</p>

<img
  src="https://roy-tian.github.io/learning-area/extras/getting-started-web/beginner-html-site/images/firefox-icon.png"
  alt="Firefox 图标" />

<h2>实时输出</h2>

<div class="output" style="min-height: 50px;"></div>

<h2>可编辑代码</h2>
<p class="a11y-label">
  按 ESC 退出编辑区域，按 Tab 可插入制表符 <code>'\t'</code>
</p>

<textarea id="code" class="input" style="min-height: 100px;width: 95%">
  &lt;p&gt;A link to my favorite website.&lt;/p&gt;
</textarea>

<div class="playable-buttons">
  <input id="reset" type="button" value="重置" />
  <input id="solution" type="button" value="显示答案" />
</div>

html {
  font-family: sans-serif;
}

h2 {
  font-size: 16px;
}

.a11y-label {
  margin: 0;
  text-align: right;
  font-size: 0.7rem;
  width: 98%;
}

body {
  margin: 10px;
  background: #f5f9fa;
}

const textarea = document.getElementById("code");
const reset = document.getElementById("reset");
const solution = document.getElementById("solution");
const output = document.querySelector(".output");
const code = textarea.value;
let userEntry = textarea.value;

function updateCode() {
  output.innerHTML = textarea.value;
}

const htmlSolution =
  '<p>A link to my <a href="https://www.mozilla.org/" title="The Mozilla homepage" target="_blank">favorite website</a>.</p>';
let solutionEntry = htmlSolution;

reset.addEventListener("click", () => {
  textarea.value = code;
  userEntry = textarea.value;
  solutionEntry = htmlSolution;
  solution.value = "显示答案";
  updateCode();
});

solution.addEventListener("click", () => {
  if (solution.value === "显示答案") {
    textarea.value = solutionEntry;
    solution.value = "隐藏答案";
  } else {
    textarea.value = userEntry;
    solution.value = "显示答案";
  }
  updateCode();
});

textarea.addEventListener("input", updateCode);
window.addEventListener("load", updateCode);

// stop tab key tabbing out of textarea and
// make it write a tab at the caret position instead

textarea.onkeydown = (e) => {
  if (e.keyCode === 9) {
    e.preventDefault();
    insertAtCaret("\t");
  }

  if (e.keyCode === 27) {
    textarea.blur();
  }
};

function insertAtCaret(text) {
  const scrollPos = textarea.scrollTop;
  let caretPos = textarea.selectionStart;

  const front = textarea.value.substring(0, caretPos);
  const back = textarea.value.substring(
    textarea.selectionEnd,
    textarea.value.length,
  );
  textarea.value = front + text + back;
  caretPos += text.length;
  textarea.selectionStart = caretPos;
  textarea.selectionEnd = caretPos;
  textarea.focus();
  textarea.scrollTop = scrollPos;
}

// Update the saved userCode every time the user updates the text area code

textarea.onkeyup = () => {
  // We only want to save the state when the user code is being shown,
  // not the solution, so that solution is not saved over the user code
  if (solution.value === "显示答案") {
    userEntry = textarea.value;
  } else {
    solutionEntry = textarea.value;
  }

  updateCode();
};

<input type="text" disabled="disabled" />

<!-- 使用 disabled 属性来防止终端用户输入文本到输入框中 -->
<input type="text" disabled />

<!-- 下面这个输入框不包含 disabled 属性，所以用户可以向其中输入 -->
<input type="text" />

<a href=https://www.mozilla.org/>favorite website</a>

<a href=https://www.mozilla.org/ title=The Mozilla homepage>favorite website</a>

<a href='https://www.example.com'>示例站点链接</a>

<a href="https://www.example.com">示例站点链接</a>

<a href="https://www.example.com'>示例站点链接</a>

<a href="https://www.example.com" title="你觉得'好玩吗'？">示例站点链接</a>

<a href='https://www.example.com' title='Isn't this fun?'>示例站点链接</a>

<a href="https://www.example.com" title="Isn't this fun?">示例站点链接</a>

<!doctype html>
<html lang="zh-CN">
  <head>
    <meta charset="utf-8" />
    <title>我的测试站点</title>
  </head>
  <body>
    <p>这是我的页面</p>
  </body>
</html>

<h2>实时输出</h2>
<div class="output" style="min-height: 50px;"></div>

<h2>可编辑代码</h2>
<p class="a11y-label">
  按 ESC 退出编辑区域，按 Tab 可插入制表符 <code>'\t'</code>
</p>
<textarea id="code" class="input" style="min-height: 100px;width: 95%">
  &lt;p&gt;相思无用，惟别而已。别期若有定，千般煎熬又何如？莫道黯然销魂，何处柳暗花明？&lt;/p&gt;
</textarea>

<div class="playable-buttons">
  <input id="reset" type="button" value="重置" />
  <input id="solution" type="button" value="显示答案" />
</div>

html {
  font-family: sans-serif;
}

h1 {
  color: blue;
}

h2 {
  font-size: 16px;
}

.a11y-label {
  margin: 0;
  text-align: right;
  font-size: 0.7rem;
  width: 98%;
}

img {
  max-width: 100%;
}

body {
  margin: 10px;
  background: #f5f9fa;
}

const textarea = document.getElementById("code");
const reset = document.getElementById("reset");
const solution = document.getElementById("solution");
const output = document.querySelector(".output");
const code = textarea.value;
let userEntry = textarea.value;

function updateCode() {
  output.innerHTML = textarea.value;
}

const htmlSolution = `<h1>经典回忆</h1>
<p>
 相思无用，惟别而已。别期若有定，千般煎熬又何如？莫道黯然销魂，何处<strong>柳暗花明</strong>？<br>
 ——《<a href="https://zh.wikipedia.org/zh-hans/神鵰俠侶">神雕侠侣</a>》
</p>
<img src="https://roy-tian.github.io/learning-area/extras/tools/playable-code/images/sdxl.jfif" alt="《神雕侠侣》作品图片">`;

let solutionEntry = htmlSolution;

reset.addEventListener("click", () => {
  textarea.value = code;
  userEntry = textarea.value;
  solutionEntry = htmlSolution;
  solution.value = "Show solution";
  updateCode();
});

solution.addEventListener("click", () => {
  if (solution.value === "显示答案") {
    textarea.value = solutionEntry;
    solution.value = "隐藏答案";
  } else {
    textarea.value = userEntry;
    solution.value = "显示答案";
  }
  updateCode();
});

textarea.addEventListener("input", updateCode);
window.addEventListener("load", updateCode);

// stop tab key tabbing out of textarea and
// make it write a tab at the caret position instead

textarea.onkeydown = (e) => {
  if (e.keyCode === 9) {
    e.preventDefault();
    insertAtCaret("\t");
  }

  if (e.keyCode === 27) {
    textarea.blur();
  }
};

function insertAtCaret(text) {
  const scrollPos = textarea.scrollTop;
  let caretPos = textarea.selectionStart;

  const front = textarea.value.substring(0, caretPos);
  const back = textarea.value.substring(
    textarea.selectionEnd,
    textarea.value.length,
  );
  textarea.value = front + text + back;
  caretPos += text.length;
  textarea.selectionStart = caretPos;
  textarea.selectionEnd = caretPos;
  textarea.focus();
  textarea.scrollTop = scrollPos;
}

// Update the saved userCode every time the user updates the text area code
textarea.onkeyup = () => {
  // We only want to save the state when the user code is being shown,
  // not the solution, so that solution is not saved over the user code
  if (solution.value === "显示答案") {
    userEntry = textarea.value;
  } else {
    solutionEntry = textarea.value;
  }

  updateCode();
};

<p>狗 狗 很 呆 萌。</p>

<p>狗 狗        很
         呆 萌。</p>

<p>HTML 中用 <p> 来定义段落元素。</p>

<p>HTML 中用 &lt;p&gt; 来定义段落元素</p>

<p>我在注释外！</p>

<!-- <p>我在注释内！</p> -->