How to properly import/export a method in node js

I am currently trying to import a method from a class to keep everything tidy since the method I plan to import will be quite long. However, I seem to get a new error every time I switch it up. The biggest issue is the import/export and the "event" parameter that don’t seem to want to work with me.

Edit: The code works if I simply combine both classes and put the method in ImportingClass.js, however it would be too much code.

ValidateInput.js:

class ValidateInput
{
    validateInput(event)
    {
        var ID = event.target.StudentID.value;
        // ...
    }
}

ImportingClass.js:

import {validateInput} from '../ValidateInput';

class ImportingClass
{

    handleSubmit(event)
    {
        validateInput(this.event);
        // ...
    }
}

Error: Uncaught TypeError: (.validateInput) is not a function

>Solution :

But we can do something like this as well

create an independent function validateInput

export function validateInput(e){
 .... code
}

and in order to call this function in your first class that is ValidateInput.js
we can do something like this

class ValidateInput{
  validateInput(){
    validateInput.apply(this, ...args)
}}

and in your second file ImportingClass.js you can import and use it
with import {validateInput} from './validateInput'

or you can export it via Prototype something like this

export const validateInput = ValidateInput.prototype.validateInput