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.
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 (New in 1.92 ) 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