What is the use of invalid selector?
The role of the invalid selector is to set a specific style when an illegal value is entered in the form element. The purpose is to remind the user that the entered value is incorrect.
The :invalid selector in CSS is mainly used Sets the specified style when the value in the form element is illegal.
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Example: When the user input is not a legal value, the style will change to a red border
<!DOCTYPE html>
<html>
<head>
<meta charset="utf-8">
<title></title>
<style>
input:invalid
{
border:2px solid red;
}
</style>
</head>
<body>
<input type="email" value="" />
<p>请输入合法 e-mail 地址，查看样式变化。</p>
</body>
</html>Rendering:
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