QS:Preg validation
From LimeSurvey Manual
Validation (using regular expressions) (preg_validation)
Description
This option lets you specify a regular expression with which to validate all parts of a question.
Starting in version 1.92, if any question or sub-question value does not meet the validation requirements, the background color of the text entry field will be changed to red so that users can easily see which parts of the question need to be corrected. Thus, you can do on-page validation and do not need to wait for the user to click submit in order to validate the question.
Valid values
- Any valid regular expression
Example
- See multiple examples here