Working with methods in JavaScript

When you work with methods that have multiple parameters, you may omit optional parameters at the end of the parameter list, but you may not omit parameters in the middle of the list. If you do not want to specify a particular parameter in the middle of the list, you must insert the value undefined to use the parameter’s default value. For example, the following definition describes the rotate() method for an art object.

rotate
  (angle
    [,changePositions]
    [,changeFillPatterns]
    [,changeFillGradients]
    [,changeStrokePattern]
    [,rotateAbout])

In the definition, taken from Adobe lllustrator CC 2017 Scripting Reference: JavaScript, optional parameters are enclosed in square brackets ( [] ).

To rotate the object 30 degrees and change the fillGradients, you would use the following script statement

myObject.rotate(30, undefined, undefined, true);

You need to specify undefined for the changePositions and changeFillPatterns parameters. You do not have to specify anything for the two optional parameters following changeFillGradients, since they are at the end of the parameter list.