Windows® 8.1 Apps with HTML5 and JavaScript Unleashed

Using the pattern Attribute

You use the pattern attribute to validate the value entered into an input field against a regular expression pattern. For example, the following HTML form validates the Social Security number against a regular expression:

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<form>    <div>        <label>            Social Security Number:            <input id="ssn"                required                pattern="^\d{3}-\d{2}-\d{4}$"                title="###-##-####" />        </label>    </div>    <div>        <input type="submit" />    </div></form>

Notice that the ssn field has both a required and pattern attribute. The pattern attribute is not triggered unless you enter a value.

Notice, furthermore, that the ssn field includes a title ...