DOM
文档对象模型是用来呈现以及与任意 HTML 或 XML 文档交互的 API 。执行下面的代码，查找并获取符合条件的指定 DOM 元素。
<!DOCTYPE html>
<html lang="zh-Hans">
<head>
<meta charset="UTF-8">
<meta name="viewport" content="width=device-width, initial-scale=1.0">
<title>JavaScript</title>
</head>
<body>
<nav id="nav">Hello World!</nav>
<div class="box">Hello JavaScript!</div>
<ul>
<li>1</li>
<li>2</li>
<li>3</li>
</ul>
<script type="text/javascript">
const nav = document.querySelector('#nav');
console.log(nav);
const box = document.querySelector('.box');
console.log(box);
const li = document.querySelector('ul li');
console.log(li);
const li1 = document.querySelector('ul li:first-child');
console.log(li1);
</script>
</body>
</html>
执行下面的代码，查找并获取符合条件的所有 DOM 元素。
<!DOCTYPE html>
<html lang="zh-Hans">
<head>
<meta charset="UTF-8">
<meta name="viewport" content="width=device-width, initial-scale=1.0">
<title>JavaScript</title>
</head>
<body>
<ul>
<li>1</li>
<li>2</li>
<li>3</li>
</ul>
<script type="text/javascript">
const li = document.querySelectorAll('ul li');
console.log(li);
</script>
</body>
</html>
执行下面的代码，使用其他方式获取 DOM 元素。
<!DOCTYPE html>
<html lang="zh-Hans">
<head>
<meta charset="UTF-8">
<meta name="viewport" content="width=device-width, initial-scale=1.0">
<title>JavaScript</title>
</head>
<body>
<nav id="nav">Hello World!</nav>
<div class="box">Hello JavaScript!</div>
<div class="box">Hello JavaScript!</div>
<ul>
<li>1</li>
<li>2</li>
<li>3</li>
</ul>
<script type="text/javascript">
const nav = document.getElementById('nav');
console.log(nav);
const box = document.getElementsByClassName('box');
console.log(box);
const li = document.getElementsByTagName('li');
console.log(li);
</script>
</body>
</html>
执行下面的代码，修改指定 DOM 元素中的 HTML 内容。
<!DOCTYPE html>
<html lang="zh-Hans">
<head>
<meta charset="UTF-8">
<meta name="viewport" content="width=device-width, initial-scale=1.0">
<title>JavaScript</title>
</head>
<body>
<nav id="nav">Hello World!</nav>
<script type="text/javascript">
const nav = document.querySelector('#nav');
console.log(nav);
nav.innerHTML = '<p>Hello JavaScript!</p>';
</script>
</body>
</html>
执行下面的代码，修改指定 DOM 元素的 CSS 属性。
<!DOCTYPE html>
<html lang="zh-Hans">
<head>
<meta charset="UTF-8">
<meta name="viewport" content="width=device-width, initial-scale=1.0">
<title>JavaScript</title>
</head>
<body>
<div class="box">Hello World!</div>
<script type="text/javascript">
const box = document.querySelector('.box');
box.style.color = 'red';
</script>
</body>
</html>
执行下面的代码，修改指定 DOM 元素的类名。
<!DOCTYPE html>
<html lang="zh-Hans">
<head>
<meta charset="UTF-8">
<meta name="viewport" content="width=device-width, initial-scale=1.0">
<title>JavaScript</title>
</head>
<body>
<div class="box">Hello World!</div>
<script type="text/javascript">
const box = document.querySelector('.box');
console.log(box.className);
box.className = 'nav';
console.log(box.className);
</script>
</body>
</html>
执行下面的代码，操作指定 DOM 元素的类名。
<!DOCTYPE html>
<html lang="zh-Hans">
<head>
<meta charset="UTF-8">
<meta name="viewport" content="width=device-width, initial-scale=1.0">
<title>JavaScript</title>
<style type="text/css">
.nav {
color: red;
}
</style>
</head>
<body>
<div class="box">Hello World!</div>
<script type="text/javascript">
const box = document.querySelector('.box');
console.log(box.className);
box.classList.add('nav');
console.log(box.className);
box.classList.remove('box');
console.log(box.className);
box.classList.toggle('box');
console.log(box.className);
</script>
</body>
</html>
执行下面的代码，修改指定 DOM 元素的自定义属性。
<!DOCTYPE html>
<html lang="zh-Hans">
<head>
<meta charset="UTF-8">
<meta name="viewport" content="width=device-width, initial-scale=1.0">
<title>JavaScript</title>
</head>
<body>
<div class="box" data-id="1">Hello World!</div>
<script type="text/javascript">
const box = document.querySelector('.box');
console.log(box.dataset);
console.log(box.dataset.id);
box.dataset.id = 233;
console.log(box.dataset);
console.log(box.dataset.id);
</script>
</body>
</html>
执行下面的代码，查找指定 DOM 元素的父节点。
<!DOCTYPE html>
<html lang="zh-Hans">
<head>
<meta charset="UTF-8">
<meta name="viewport" content="width=device-width, initial-scale=1.0">
<title>JavaScript</title>
</head>
<body>
<nav class="nav">
<div class="box"></div>
</nav>
<script type="text/javascript">
const box = document.querySelector('.box');
console.log(box.parentNode);
</script>
</body>
</html>
执行下面的代码，查找指定 DOM 元素的所有子节点。
<!DOCTYPE html>
<html lang="zh-Hans">
<head>
<meta charset="UTF-8">
<meta name="viewport" content="width=device-width, initial-scale=1.0">
<title>JavaScript</title>
</head>
<body>
<ul>
<li>1</li>
<li>2</li>
<li>3</li>
</ul>
<script type="text/javascript">
const ul = document.querySelector('ul');
console.log(ul.children);
</script>
</body>
</html>
执行下面的代码，查找指定 DOM 元素的兄弟节点。
<!DOCTYPE html>
<html lang="zh-Hans">
<head>
<meta charset="UTF-8">
<meta name="viewport" content="width=device-width, initial-scale=1.0">
<title>JavaScript</title>
</head>
<body>
<ul>
<li>1</li>
<li class="li">2</li>
<li>3</li>
</ul>
<script type="text/javascript">
const li = document.querySelector('.li');
console.log(li.previousElementSibling);
console.log(li.nextElementSibling);
</script>
</body>
</html>
执行下面的代码，创建新的 DOM 节点并插入。
<!DOCTYPE html>
<html lang="zh-Hans">
<head>
<meta charset="UTF-8">
<meta name="viewport" content="width=device-width, initial-scale=1.0">
<title>JavaScript</title>
</head>
<body>
<ul>
<li>1</li>
<li>2</li>
<li>3</li>
</ul>
<script type="text/javascript">
const div = document.createElement('div');
document.body.appendChild(div);
const ul = document.querySelector('ul');
const p = document.createElement('p');
ul.insertBefore(p, ul.children[0]);
</script>
</body>
</html>
执行下面的代码，克隆指定节点并插入。
<!DOCTYPE html>
<html lang="zh-Hans">
<head>
<meta charset="UTF-8">
<meta name="viewport" content="width=device-width, initial-scale=1.0">
<title>JavaScript</title>
</head>
<body>
<div></div>
<ul>
<li>1</li>
<li>2</li>
<li>3</li>
</ul>
<script type="text/javascript">
const div = document.querySelector('div');
const ul = document.querySelector('ul');
const new_ul = ul.cloneNode(true);
div.appendChild(new_ul);
</script>
</body>
</html>
执行下面的代码，删除指定节点。
<!DOCTYPE html>
<html lang="zh-Hans">
<head>
<meta charset="UTF-8">
<meta name="viewport" content="width=device-width, initial-scale=1.0">
<title>JavaScript</title>
</head>
<body>
<ul>
<li>1</li>
<li>2</li>
<li>3</li>
</ul>
<script type="text/javascript">
const ul = document.querySelector('ul');
ul.removeChild(ul.children[0]);
</script>
</body>
</html>