Validating xhtml code

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It is a common maxim in security to trust nobody, hence never trust the user to enter correct or valid form values.For example, in an email form field, instead of entering a valid email address, the user might enter an invalid one or malicious data obviously ignoring the intent of the request.Telephone numbers: As mentioned, the See the Pen Alpha-Numeric Character Validation Example by Site Point (@Site Point) on Code Pen.Twitter Username This regular expression matches a Twitter username with the leading @ symbol.But that is changing or rather has changed because validation can now be done using HTML5 without having to write complex Java Script validation code.HTML5 includes a fairly solid form validation mechanism powered by the following .In most cases, however, you should be able to use Google to search for the regular expression you want, or even use a tool to help you.

This attribute specifies a format (in the form of a Java Script Regular Expression) that the field value is checked against.Example: attribute, so you can test those by trying to submit any of the forms without entering anything in the field.Browser support for form validation features is pretty strong, and you can easily polyfill them where necessary.Start now and learn what is possible with HTML email.This course was created and produced by Chris Converse.

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