Set an html5 pattern on a Caldera Forms field

cf-html5pattern-example.php

<?php
/*
 * HTML5 Pattern to limiot input field to 8 alphanumeric (only capitals) characters
 */
 add_filter( 'caldera_forms_field_attributes', function($attrs, $field){
	//IMPORTANT - Change your field ID
	if ( 'fld_1234' === $field[ 'ID'] ) {
		$attrs[ 'pattern' ] = '[A-Z0-9]{8}';
	}
	return $attrs;
}, 10, 2 );