Disable yup validation based on external variable

gistfile1.txt

 //external variable
 const disabledEndYear = true
 
//schema validation for yup
 const schema = yup
    .object({
      field_name: yup.number().when([], {
        is: (val: any) => {
          return !disabledEndYear; //if false
        },
        then: yup
          .number()
          .label("Field name")
          .typeError("Field must be a number")
          .transform((value) => (isNaN(value) ? undefined : value))
          .required(),
        otherwise: yup
          .number()
          .transform((value) => (isNaN(value) ? undefined : value))
          .nullable(),
      }),
    })
    .required();