Validating a website
This is particularly important for actions that are permanent or otherwise critical, but also when data cannot be automatically checked.For example, providing users with the option to check the postal address that they provided can be useful before a purchase is completed.In general, client-side validation results in a better user experience and makes resolving validation errors more understandable. However, not all web browsers support HTML5, or they may not support your custom validation scripts.
In the example below, the attribute is added to the input field.
Also, the attribute can be added to form controls, to programmatically indicate that they are required.
Most current web browsers support this attribute and will communicate missing required input to the user, using standard web browser dialog mechanisms.
This is useful for specific types of data patterns such as telephone numbers, postal codes, and serial numbers.
In the example below, the element specifies a particular format that matches car license plate (registration) numbers in Germany.
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Most current web browsers support these features and handle input validation.