The definition of valid, invalid and required in html5_html5 tutorial skills

css3 prompt only applies to advanced browsers:

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IE9

The definitions of valid, invalid, and required

The code is as follows

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The code is as follows:

input:required, input:valid, input: invalid{border:0 none; outline: 0 none; -webkit-box-shadow:none; -moz-box-shadow:none; -ms-box-shadow:none; -o-box-shadow:none; box- shadow: none;}

In the past, verification forms would use js and regular expressions to determine whether the filled-in content was correct, such as email verification.

The emergence of HTML5 provides us with some attributes, so we can solve this inspection form content without writing js and regular expressions.
:required
Must, that means the input cannot be empty.

:valid
is valid, that is, it is triggered when the filled in content meets the requirements.

:invalid
Invalid, which is triggered when the filled in content does not meet the requirements.