SurveyToGo: Introduction to Regular Expressions (RegEx)

Introduction to Regular Expressions (RegEx)—explains patterns used to validate phone numbers, ID codes, and other text formats in open-ended questions.

Aug 4, 2026
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Introduction to Regular Expressions (RegEx)

Overview

Regular expressions (RegEx) are patterns of characters used to determine whether a piece of text matches a specified format.

Common uses for regular expressions include validating phone numbers, identification numbers, ZIP/postal codes, and email addresses entered into Open Ended questions during an interview.

Using Regular Expressions

SurveyToGo provides the built-in dblIsRegEx() function to validate text against a regular expression.

The function accepts two parameters:

Regular expression – The RegEx pattern to validate against.
Text – The text to be validated.

The function returns:

true if the text matches the specified regular expression.
false if the text does not match the specified regular expression.

Example: Validating an Email Address

The following is an example of a regular expression that validates email addresses:

^[_A-Za-z0-9-]+(\.[_A-Za-z0-9-]+)*@[A-Za-z0-9]+(\.[A-Za-z0-9]+)*(\.[A-Za-z]{2,})$

Note: This example is provided for demonstration purposes only. SurveyToGo includes the built-in function IsEMail(Answer(CurrQues)), which is the recommended way to validate email addresses.

Suppose you have an Open Ended question that asks respondents to enter their email address. To validate the response using a Validation Rule, use the following condition:

!dblIsRegEx("^[_A-Za-z0-9-]+(\\.[_A-Za-z0-9-]+)*@[A-Za-z0-9]+(\\.[A-Za-z0-9]+)*(\\.[A-Za-z]{2,})$", Answer(CurrQues))

This validation rule returns true when the entered email address does not match the specified pattern, causing the validation to fail and prompting the respondent to enter a valid email address.

If an invalid email address is entered, an error message will appear and the interview will not be allowed to proceed.

Important: When writing a regular expression, remember that it is passed to dblIsRegEx() as a string parameter.

Because of this, any backslash (\) used in the regular expression must be escaped by writing it twice (\\).

For example, the following regular expression matches a single non-digit character:

^\D$

However, when used in a SurveyToGo validation rule, it must be written as:

!dblIsRegEx("^\\D$", Answer(CurrQues));

In general, replace every \ in your regular expression with \\ when passing it as a string to dblIsRegEx().

For quick reference of the syntax and testing your regular expressions we recommend the following site:

https://rubular.com/

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SurveyToGo-Introduction-to-Regular-Expressions-RegEx