For more information beyond this tutorial, see the Constraint validation guide. When you enter data, the web application checks it to see that the data is correct.
If the information is correct, the application allows the data to be submitted to the server and (usually) saved in a database; if the information isn't correct, it gives you an error message explaining what needs to be corrected.
The message is shown to the user when reporting the problem.
For legacy browsers, it's possible to use a polyfill such as Hyperform to compensate for the lack of support for the constraint validation API.
Because you're already using Java Script, using a polyfill isn't an added burden to your website or web application's design or implementation.
Validation attributes allow you to specify rules for a form input, such as whether a value must be filled in; the minimum and maximum length of the data; whether the data needs to be a number, an email address, or something else; and a pattern that the data must match.
If the entered data follows all of the specified rules, it is considered valid; if not, it is considered invalid.
User-submitted data should also be verified using a secure server-side script.
Otherwise a browser with Java Script disabled, or a hacker trying to compromise your site, can easily by-pass client-side validation.When the form is submitted - either by hitting Enter or clicking on the Submit button - the to abort (cancel) the form submission. In a real-life situation you will most likely have more fields to check, and more complicated conditions, but the principle remains the same.All you need to do is extend the command, in which case the form will be submitted.Validating form input with Java Script is easy to do and can save a lot of unnecessary calls to the server.It can prevent people from leaving fields blank, from entering too little or too much or from using invalid characters.For an alternative approach to client-side form validation, without Java Script, check out our new article on HTML5 Form Validation which is available now in most modern browsers. The first test in the example is therefore only necessary in order to provide a different error message when the input is blank.Tags: Adult Dating, affair dating, sex dating