Are you getting this error message on your Zoho Creator application? If so, do not worry is easy fixable and most of the times its due to the lack of a referenced table data within the Form you are trying to update.
Most of the times the main cause for GENERATEJS_TASK error is caused when we are trying to open a Form using a function that delivers ID parameters to specific fields within the form. You can update a value on a dropdown but you can not reference that parameter to update a field within a subform or other table within the existing Form. You must first fetch the corresponding data before you can update subform fields.
Lets take a look at the below example. Assume you are working with Form A, which has Filed1, Field2 within Form A you have subform Aa & need to update Subfield1 & Subfield2.
Parameters will travel on your url ID & update Form A Fields1 & 2
https://creator.zoho.com/userid/yourappname/#Form:NameFormA?Field1=1593428000001420284&Field2=1593428000001420288
// First Need to Fetch the corresponding table "On Add/On Load" section of your Form.
T1 = Table1 ;
T2 = Table2 ;
//Now that you have the corresponding data you can update values within a subform.
SubformAa.subfield1 = T1.ID; SubfomrAa.subfield2 = T2.ID;
There are other events that can cause this error to break your app flow. however, this is in my experience the most common one I have seen. Enjoy!!!