HTML5 Form Attributes (Part 2)

The following is an extract from our book, HTML5 & CSS3 for the Real World, 2nd Edition, written by Alexis Goldstein, Louis Lazaris, and Estelle Weyl. Copies are sold in stores worldwide, or you can buy it in ebook form here.

The pattern Attribute

The pattern attribute enables you to provide a regular expression that the user’s input must match in order to be considered valid. For any input where the user can enter free-form text, you can limit what syntax is acceptable with the pattern attribute.

The regular expression language used in patterns is the same Perl-based regular expression syntax as JavaScript, except that the pattern attribute must match the entire value, not just a subset. When including a pattern, you should always indicate to users what is the expected (and required) pattern.

The global title attribute has special significance when used in conjunction with the pattern attribute. Since browsers currently show the value of the title attribute on hover such as a tooltip, include pattern instructions that are more detailed than placeholder text, and which form a coherent statement. That title attribute will also be displayed with the browser’s default error message in browsers that support native form validation with error messaging, which we’ll cover later in this chapter.

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by Alexis Goldstein via SitePoint