TypeError: undefined is not a function

Script Include class or function name is misspelled or the Script Include does not exist in the system. (high likelihood)

GlideRecord query returns no results and script attempts to call methods on the empty result without checking if record exists. (high likelihood)

Function or method name contains a typo when calling built-in ServiceNow API methods or custom functions. (high likelihood)

Script Include is not accessible due to incorrect access scope settings or missing application dependencies. (medium likelihood)

Variable is declared but not initialized before attempting to call a method on it in the script logic. (medium likelihood)

Step 1: Check the System Log at System Diagnostics > Log > Application Log to identify the exact line number and script where the error occurs.

Step 2: Examine the failing script line to identify which variable or object is undefined when the method is being called.

Step 3: If calling a Script Include, verify it exists in System Definition > Script Includes and check for spelling errors in the class name.

Step 4: For GlideRecord operations, add null checks using if(gr.next()) or if(gr.isValidRecord()) before calling methods on the record object.

Step 5: Verify function names against ServiceNow API documentation and check for typos in method names like getValue(), setValue(), or update().

Step 6: If using Script Includes across applications, check the Accessible from field is set to All application scopes or verify application dependencies are configured.

Step 7: Add defensive coding by checking if variables are defined using typeof variable !== 'undefined' before calling methods on them.

Step 8: Test the corrected script in the Background Scripts module at System Definition > Scripts - Background to verify the fix works.