- 在 JavaScript 中 HTML 标签也称之为
DOM 元素- 使用
document 的时候前面不用加 window例如下面的一个小示例
<html lang="en">
<head>
<meta charset="UTF-8">
<title>demo</title>
<script>
var num = 666;
console.log(window.num);
console.log(num);
</script>
</head>
<body>
</body>
</html>
document 同理可证
<html lang="en">
<head>
<meta charset="UTF-8">
<title>demo</title>
<script>
console.log(window.document);
console.log(document);
</script>
</head>
<body>
</body>
</html>
通过 id 获取指定元素
- 由于
id 不可以重复，所以找到了就会将找到的标签包装成一个对象返回给我们，找不到就返回Null - 注意点：DOM 操作返回的是一个对象，这个对象是宿主类型对象 (浏览器提供的对象)
<html lang="en">
<head>
<meta charset="UTF-8">
<title>demo</title>
</head>
<body>
<div class="father">
<form>
<input type="text" name="username"/>
<input type="password" name="password"/>
</form>
</div>
<div class="father" id="box">我是div</div>
<script>
let oDiv = document.getElementById("box");
console.log(oDiv);
console.log(typeof oDiv);
</script>
</body>
</html>
通过 class 名称获取
- 由于
class 可以重复，所以找到了就返回一个存储了标签对象的数组，找不到就返回一个空数组
<html lang="en">
<head>
<meta charset="UTF-8">
<title>demo</title>
</head>
<body>
<div class="father">
<form>
<input type="text" name="username"/>
<input type="password" name="password"/>
</form>
</div>
<div class="father" id="box">我是div</div>
<script>
let oDivs = document.getElementsByClassName("father");
console.log(oDivs);
</script>
</body>
</html>
通过 name 名称获取
- 由于
name 可以重复，所以找到了就返回一个存储了标签对象的数组，找不到就返回一个空数组 - 注意点：
getElementsByName 在不同的浏览器中工作的方式不同。在IE 和Opera 中，getElementsByName() 方法还会返回那些 id 为指定值的元素
<html lang="en">
<head>
<meta charset="UTF-8">
<title>demo</title>
</head>
<body>
<div class="father">
<form>
<input type="text" name="test"/>
<input type="password" name="test"/>
</form>
</div>
<div class="father" id="box">我是div</div>
<script>
let oDivs = document.getElementsByName("test");
console.log(oDivs);
</script>
</body>
</html>
通过标签名称获取
- 由于标签名称可以重复，所以找到了就返回一个存储了标签对象的数组，找不到就返回一个空数组
<html lang="en">
<head>
<meta charset="UTF-8">
<title>demo</title>
</head>
<body>
<div class="father">
<form>
<input type="text" name="test"/>
<input type="password" name="test"/>
</form>
</div>
<div class="father" id="box">我是div</div>
<script>
let oDivs = document.getElementsByTagName("div");
console.log(oDivs);
</script>
</body>
</html>
通过选择器获取
-
querySelector 只会返回根据指定选择器找到的第一个元素
<html lang="en">
<head>
<meta charset="UTF-8">
<title>demo</title>
</head>
<body>
<div class="father">
<form>
<input type="text" name="test"/>
<input type="password" name="test"/>
</form>
</div>
<div class="father" id="box">我是div</div>
<script>
let oDivOne = document.querySelector("#box");
let oDivTwo = document.querySelector(".father");
let oDivThree = document.querySelector("div>form");
console.log(oDivOne);
console.log(oDivTwo);
console.log(oDivThree);
</script>
</body>
</html>
-
querySelectorAll 会返回指定选择器找到的所有元素
<html lang="en">
<head>
<meta charset="UTF-8">
<title>demo</title>
</head>
<body>
<div class="father">
<form>
<input type="text" name="test"/>
<input type="password" name="test"/>
</form>
</div>
<div class="father" id="box">我是div</div>
<script>
let oDivs = document.querySelectorAll(".father");
console.log(oDivs);
</script>
</body>
</html>
获取指定元素所有的子元素
-
children 属性获取到的是指定元素中所有的子元素
<html lang="en">
<head>
<meta charset="UTF-8">
<title>demo</title>
</head>
<body>
<div>
<h1>1</h1>
<h2>2</h2>
<p class="item">3</p>
<p>4</p>
<span>5</span>
</div>
<script>
let oDiv = document.querySelector("div");
console.log(oDiv.children);
</script>
</body>
</html>
-
childNodes 属性获取到的是指定元素中所有的节点
<html lang="en">
<head>
<meta charset="UTF-8">
<title>demo</title>
</head>
<body>
<div>
<h1>1</h1>
<h2>2</h2>
<p class="item">3</p>
<p>4</p>
<span>5</span>
</div>
<script>
let oDiv = document.querySelector("div");
console.log(oDiv.childNodes);
</script>
</body>
</html>
<html lang="en">
<head>
<meta charset="UTF-8">
<title>demo</title>
</head>
<body>
<div>
<h1>1</h1>
<h2>2</h2>
<p class="item">3</p>
<p>4</p>
<span>5</span>
</div>
<script>
let oDiv = document.querySelector("div");
for (let node of oDiv.childNodes) {
// console.log(node.nodeType);
if (node.nodeType === Node.ELEMENT_NODE) {
console.log(node);
}
}
</script>
</body>
</html>
什么是节点
- DOM 对象(document)，这个对象以树的形式保存了界面上所有的内容
- HTML 页面每一部分都是由节点(标签(元素)、文本、属性)
获取指定节点中的第一个子节点
<html lang="en">
<head>
<meta charset="UTF-8">
<title>demo</title>
</head>
<body>
<div>
<h1>1</h1>
<h2>2</h2>
<p class="item">3</p>
<p>4</p>
<span>5</span>
</div>
<script>
let oDiv = document.querySelector("div");
console.log(oDiv.firstChild);
</script>
</body>
</html>
获取指定元素中的第一个子元素
<html lang="en">
<head>
<meta charset="UTF-8">
<title>demo</title>
</head>
<body>
<div>
<h1>1</h1>
<h2>2</h2>
<p class="item">3</p>
<p>4</p>
<span>5</span>
</div>
<script>
let oDiv = document.querySelector("div");
console.log(oDiv.firstElementChild);
</script>
</body>
</html>
获取指定节点中最后一个子节点
<html lang="en">
<head>
<meta charset="UTF-8">
<title>demo</title>
</head>
<body>
<div>
<h1>1</h1>
<h2>2</h2>
<p class="item">3</p>
<p>4</p>
<span>5</span>
</div>
<script>
let oDiv = document.querySelector("div");
console.log(oDiv.lastChild);
</script>
</body>
</html>
获取指定元素中最后一个子元素
<html lang="en">
<head>
<meta charset="UTF-8">
<title>demo</title>
</head>
<body>
<div>
<h1>1</h1>
<h2>2</h2>
<p class="item">3</p>
<p>4</p>
<span>5</span>
</div>
<script>
let oDiv = document.querySelector("div");
console.log(oDiv.lastElementChild);
</script>
</body>
</html>
通过子元素获取父元素/父节点
<html lang="en">
<head>
<meta charset="UTF-8">
<title>demo</title>
</head>
<body>
<div>
<h1>1</h1>
<h2>2</h2>
<p class="item">3</p>
<p>4</p>
<span>5</span>
</div>
<script>
let item = document.querySelector(".item");
console.log(item.parentElement);
console.log(item.parentNode);
let parentEle = item.parentElement || item.parentNode;
console.log(parentEle);
</script>
</body>
</html>
获取相邻上一个节点
<html lang="en">
<head>
<meta charset="UTF-8">
<title>demo</title>
</head>
<body>
<div>
<h1>1</h1>
<h2>2</h2>
<p class="item">3</p>
<p>4</p>
<span>5</span>
</div>
<script>
let item = document.querySelector(".item");
console.log(item.previousSibling);
</script>
</body>
</html>
获取相邻上一个元素
<html lang="en">
<head>
<meta charset="UTF-8">
<title>demo</title>
</head>
<body>
<div>
<h1>1</h1>
<h2>2</h2>
<p class="item">3</p>
<p>4</p>
<span>5</span>
</div>
<script>
let item = document.querySelector(".item");
console.log(item.previousElementSibling);
</script>
</body>
</html>
获取相邻下一个节点
<html lang="en">
<head>
<meta charset="UTF-8">
<title>demo</title>
</head>
<body>
<div>
<h1>1</h1>
<h2>2</h2>
<p class="item">3</p>
<p>4</p>
<span>5</span>
</div>
<script>
let item = document.querySelector(".item");
console.log(item.nextSibling);
</script>
</body>
</html>
获取相邻下一个元素
<html lang="en">
<head>
<meta charset="UTF-8">
<title>demo</title>
</head>
<body>
<div>
<h1>1</h1>
<h2>2</h2>
<p class="item">3</p>
<p>4</p>
<span>5</span>
</div>
<script>
let item = document.querySelector(".item");
console.log(item.nextElementSibling);
</script>
</body>
</html>
