CSS 伪类选择器 :indeterminate 表示状态不确定或未知的元素。
更具体地说， :indeterminate 伪类面向以下元素：
:indeterminate下面是一个示例：不确定的伪类，用于 checkox 和单选按钮：
<html>
<head>
<style>
input[type="checkbox"]:indeterminate {
box-shadow: 0 0 5px 5px rgb(224, 5, 5);
}
input[type="radio"]:indeterminate {
box-shadow: 0 0 5px 5px rgb(17, 235, 28);
}
div {
padding: 10px;
}
</style>
</head>
<body>
<h2>:indeterminate selector example</h2>
<form>
<div>
<input type="checkbox" id="box"> Checkbox
</div>
<div>
<input type="radio" id="box1"> Radio
</div>
<script>
var checkbox=document.getElementById("box");
checkbox.indeterminate=true;
var radio=document.getElementById("box1");
radio.indeterminate=true;
</script>
</form>
</body>
</html>下面是一个示例 :indeterminate pseudo-class for radio button group：
<html>
<head>
<style>
label {
margin-right: .5em;
position: relative;
top: 1px;
}
input[type="radio"]:indeterminate + label {
color: magenta;
font-size: larger;
}
form {
border: 3px solid black;
width: 500px;
}
</style>
</head>
<body>
<h2>:indeterminate selector example</h2>
<form>
<p>The state of radio button group is indeterminate, hence CSS styling applied.</p>
<p>Select any radio button and see the change:</p>
<input type="radio" name="option" value="true" id="true">
<label for="true">True</label>
<input type="radio" name="option" value="false" id="false">
<label for="false">False</label>
<input type="radio" name="option" value="unknown" id="unknown">
<label for="unknown">Unknown</label>
</form>
</body>
</html>下面是一个示例：indeterminate pseudo-class for progress element：
<html>
<head>
<style>
progress {
margin: 8px;
}
progress:indeterminate {
width: 300px;
height: 50px;
}
</style>
</head>
<body>
<h2>:indeterminate selector example - progress</h2>
<progress></progress>
</body>
</html>
