pentaho/pentaho-kettle · error · JavaScriptException

The function call month requires 1 argument.

Error message

The function call month requires 1 argument.

What it means

The month() JavaScript function returns the calendar month of a Date argument as a number (0-based, per java.util.Calendar.MONTH). It throws this runtime error when not called with exactly one argument.

Solutions

1. Call month() with exactly one Date argument.
2. Convert string dates with str2Date() before calling month().
3. Null-check the field; note the result is 0-based (add 1 for human-readable month).
4. Verify the field type is Date in the step's field definitions.

Example fix

// before
var m = month();
// after
var m = month(myDateField) + 1; // Calendar.MONTH is 0-based

if (myDateField == null) throw 'month: date is null';
var m = month(myDateField) + 1; // 0-based

function isDate(v) { return v != null && v.getClass && String(v.getClass()) === 'class java.util.Date'; }

try { var m = month(myDateField) + 1; } catch (e) { var m = null; }

When it happens

Trigger: Calling month() with zero or multiple arguments in a modified JavaScript step; or with an argument that fails the Date conversion, which is then re-thrown as e.toString().

Common situations: Forgetting the date field argument, passing a date string without str2Date(), or expecting 1-based month semantics and misreading the result afterwards.

Understand the failure class

Background: "missing required argument" and "the following required arguments were not provided": what required-argument errors mean and how to fix them — this error's family across 20 libraries.

Related errors

• The function call quarter requires 1 argument.
• The function call week requires 1 argument.
• The function call year requires 1 argument.
• Error in isEmpty function:
• Script.Log.CouldNotAddDefaultConstants

AI-assisted analysis of pentaho/pentaho-kettle@f3058517a1 (2026-09-13). Data as JSON: /api/errors/f47ed028948cffb7. Report an issue: GitHub.

Appendix: source

Thrown at engine/src/main/java/org/pentaho/di/trans/steps/scriptvalues_mod/ScriptValuesAddedFunctions.java:892

      throw Context.reportRuntimeError( e.toString() );
    }
  }

  public static Object month( Context actualContext, Scriptable actualObject, Object[] ArgList,
    Function FunctionContext ) {
    try {
      if ( ArgList.length == 1 ) {
        if ( isNull( ArgList[0] ) ) {
          return new Double( Double.NaN );
        } else if ( isUndefined( ArgList[0] ) ) {
          return Context.getUndefinedValue();
        }
        java.util.Date dArg1 = (java.util.Date) Context.jsToJava( ArgList[0], java.util.Date.class );
        Calendar cal = Calendar.getInstance();
        cal.setTime( dArg1 );
        return new Double( cal.get( Calendar.MONTH ) );
      } else {
        throw Context.reportRuntimeError( "The function call month requires 1 argument." );
      }
    } catch ( Exception e ) {
      throw Context.reportRuntimeError( e.toString() );
    }

  }

  public static Object quarter( Context actualContext, Scriptable actualObject, Object[] ArgList,
    Function FunctionContext ) {
    try {
      if ( ArgList.length == 1 ) {
        if ( isNull( ArgList[0] ) ) {
          return new Double( Double.NaN );
        } else if ( isUndefined( ArgList[0] ) ) {
          return Context.getUndefinedValue();
        }
        java.util.Date dArg1 = (java.util.Date) Context.jsToJava( ArgList[0], java.util.Date.class );
        Calendar cal = Calendar.getInstance();

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