查询单个元素document.getElementById
示例
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<!DOCTYPE html>
<html>
<head>
<title>访问元素</title>
<meta charset="UTF-8">
<meta name="viewport" content="width=device-width, initial-scale=1.0">
<style>
.mycolor{
color:#fff;
}
</style>
</head>
<body>
<ul id="ul">
<li id="a">油条</li>
<li id="b">包子</li>
<li id="c">米饺</li>
<li id="d"><a>鱼粉</a></li>
</ul>
<script>
// 返回单一元素节点
var el = document.getElementById('a');
el.className='mycolor';
</script>
</body>
</html>
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按CSS查询一个 document.querySelector
按CSS查询
示例1 查询一个
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<!DOCTYPE html>
<html>
<head>
<title>访问元素</title>
<meta charset="UTF-8">
<meta name="viewport" content="width=device-width, initial-scale=1.0">
<style>
.mycolor{
color:#fff;
}
.steam{
text-decoration: initial;
}
</style>
</head>
<body>
<ul id="ul">
<li id="a">油条</li>
<li id="b" class="steam">包子</li>
<li id="c" class="steam">米饺</li>
<li id="d"><a>鱼粉</a></li>
</ul>
<script>
// 返回一个元素节点
var el = document.querySelector('li.steam');
el.className='mycolor';
</script>
</body>
</html>
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示例2 查询多个
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<!DOCTYPE html>
<html>
<head>
<title>访问元素</title>
<meta charset="UTF-8">
<meta name="viewport" content="width=device-width, initial-scale=1.0">
<style>
.mycolor{
color:#fff;
}
.steam{
text-decoration: initial;
}
</style>
</head>
<body>
<ul id="ul">
<li id="a">油条</li>
<li id="b" class="steam">包子</li>
<li id="c" class="steam">米饺</li>
<li id="d"><a>鱼粉</a></li>
</ul>
<script>
// 返回多个元素节点
var els = document.querySelectorAll('li.steam');
els[0].className='mycolor';
</script>
</body>
</html>
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按元素标签查询多个 getElementsByTagName
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<!DOCTYPE html>
<html>
<head>
<title>访问元素</title>
<meta charset="UTF-8">
<meta name="viewport" content="width=device-width, initial-scale=1.0">
<style>
.mycolor{
color:#fff;
}
.steam{
text-decoration: initial;
}
</style>
</head>
<body>
<ul id="ul">
<li id="a">油条</li>
<li id="b" class="steam">包子</li>
<li id="c" class="steam">米饺</li>
<li id="d"><a>鱼粉</a></li>
</ul>
<script>
// 按元素标签查询
var els = document.getElementsByTagName('li');
els[2].className='mycolor';
</script>
</body>
</html>
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查询父节点parentNode
示例
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<!DOCTYPE html>
<html>
<head>
<title>访问元素</title>
<meta charset="UTF-8">
<meta name="viewport" content="width=device-width, initial-scale=1.0">
<style>
.mycolor{
color:#fff;
}
.steam{
text-decoration: initial;
}
</style>
</head>
<body>
<ul id="ul">
<li id="a">油条</li>
<li id="b" class="steam">包子</li>
<li id="c" class="steam">米饺</li>
<li id="d" ><a id="yufen">鱼粉</a></li>
</ul>
<script>
// 查找父节点
var el = document.getElementById('yufen');
el.parentNode.className="mycolor";
</script>
</body>
</html>
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查找兄弟元素 previousSibling nextSibling
示例
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<!DOCTYPE html>
<html>
<head>
<title>访问元素</title>
<meta charset="UTF-8">
<meta name="viewport" content="width=device-width, initial-scale=1.0">
<style>
.mycolor{
color:#fff;
}
.steam{
color: red;
}
</style>
</head>
<body>
<ul id="ul">
<li id="ali">油条</li><li id="bli">包子</li><li id="cli">米饺</li><li id="dli"><a id="yufen">鱼粉</a></li>
</ul>
<script>
// 查找父节点
var tempel = document.getElementById("bli");
tempel.className="steam";
var previousNode = tempel.previousSibling;
previousNode.className="mycolor";
var nextNode = tempel.nextSibling;
nextNode.className="mycolor";
</script>
</body>
</html>
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兄弟元素查找比较坑，只是能元素在同一行时才能查询。
查询子节点 firstChild lastChild
示例
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<!DOCTYPE html>
<html>
<head>
<title>访问元素</title>
<meta charset="UTF-8">
<meta name="viewport" content="width=device-width, initial-scale=1.0">
<style>
.mycolor{
color:#fff;
}
.steam{
color: red;
}
</style>
</head>
<body>
<ul id="ul"
><li id="ali">油条</li
><li id="bli">包子</li
><li id="cli"><a id="yufen">米饺</a></li
><li id="dli">鱼粉</li
></ul>
<script>
// 查找子节点
var tempel = document.getElementById("ul");
var firstNode = tempel.firstChild;
firstNode.className = "mycolor";
var lastNode = tempel.lastChild;
lastNode.className = "mycolor";
</script>
</body>
</html>
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注意，<ul></ul>这段代码，要写成这样才正常查询到。