You can apply advanced validation to check responses against certain “patterns” or “regular expressions” (RegEx) by using the form designer's regex() function, e.g. =regex(string value, string expression). This function returns result of applying the given regex expression to the given value.
Regular expressions use a powerful syntax which you can use to build very complex patterns. See the cheat sheet attached to this article for a reference or try RegExr, a free online tool to help you build your own regular expressions.
Some examples of RegEx:
| RegEx examples | Explanation | Successful input |
|---|---|---|
| taken | Validates whether the response contains the string "taken". | Undertaken |
| ^taken | Validates whether the response starts with the string "taken". | taken over |
| ^taken$ | Validates whether the response matches the string "taken" exactly. | taken |
| ^[0-9]{4}$ | Validates whether the response is exactly 4 digits in length. | 0063 |
| ^[0-9]{4,10}$ | Validates whether the response is a 4 to 10 digit number. | 1234567890 |
| ^[vVbB][0-9]{6}$ | Validates whether the response begins with either the letter 'V' or 'B' (upper or lower case) followed by a 6-digit number. | B123456 |
| ^[0-9]{2}-[0-9]{6,7}\s[a-zA-Z]\s[0-9]{2}$ | Validates whether the response starts with two digits, a dash, and then six or seven digits; after the 6/7 string of digits there is always a space, then a letter then a space and finally two more digits; not case sensitive). | 07-1234567 G 01 |
| ^(\+?27|0)[6-9][1-7][0-9]{7}$ | Validates whether the response is a South African mobile number (including the leading international dialling code). | 0828091234 |
Example:
Adding validation to a field to ensure the mobile number that is entered is exactly 10 digits long.
- Create a new Text field to capture the participant's mobile number. (Note: the Text field type should be used instead of the Number field type for capturing numeric identifiers)
- Click on the Validation tab.
- Click the 'Configure validation rules' button (if no rules have been set up yet).
- Select that the response will only be valid when 'all' of the criteria are met.
- Select that the response must be 'equal to' the criteria.
- Use the regex function to specify the regular expression rules: The first parameter is a reference to the current field ("$Text_field_3") as the 'value', and the second parameter contains the regular expression to evaluate the value against, in this case "^[0-9]{10}$".
- Additional validation criteria can be added as needed below.
Hint: Test your validation rules by using the 'Preview' button on the far right in your top toolbar.
Using the legacy form designer? Have a look at the article on advanced validation in the legacy form designer.
