The Low Down
pattern attribute, you can declare your own requirements for validation using Regular Expressions.
- Relevant for the
text, search, url, tel, email, and
passwordtypes: the input types that allow for freeform data entry and don’t have predefined patterns the values must match.
- The value of the
patternattribute is a regular expression that must match the entire value of the input.
- The empty string is considered valid (no misMatch) unless the
requiredattribute is present as well (valueMissing).
- The regular expression must match the entire value, not just a section of the value, as if it started with ^
and ended with
multipleattributes, remember that the pattern must match the entire value!
- Use the
titleattribute to describe what pattern you expect, as per the spec. When the
patternattribute is included, the item’s
titleattribute gets special meaning. If there is a patternMismatch during constraint validation , the
titlevalue will be included as content in the error bubble displayed in supporting browsers – as displayed to the left (“Enter 3 characters” was the
title). That’s why the previous point — describe the pattern you expect, not the purpose of the input — is important to remember.
- If the
patternattribute is present, the non-empty value must match the pattern attribute. If the value does not match the regular expression, the patternMismatch constraint validation error message and title will be displayed in the error bubble upon form submission.
- Resource of useful patterns
- Android, Safari and Mobile Safari support the
patternattribute, but do not support form validation, so will not prevent an incorrect value from being submitted, but do support the UI pseudoclasses.