SyntaxError: ambiguous indirect export: default Error when importing my own class

Use braces {} around your import Name

// ..classes/formValidatorClass.js // Comment: => suggestion change your file name to similar your class name
export class FormValidator {
...
}

// some vue file with a form
// import FormValidation from "..classes/formValidationClass"
import { FormValidator as FormValidation} from "../classes/formValidatorClass"; // Comment: => use brackets around your import name. if you want use FormValidation you can use also a alias (`originalName as newName`)

export default {...}