I've just finished a lengthy debugging session and while I solved the issue, I have no idea why my solution is necessary.

I have a file Update.js that looks like this:

class Update {

  static doThisAfterClick = (event) => {
    console.log("First button clicked!");
  }

  static doThisWhenCalled = (name, age) => {
    console.log("My name is " + name + " and my age is " + age);
  }
}

export default Update;

In Edit.js I import the module:

let Update = require('./Update');

class Edit {

  static fancyEventHandler = (event) => {
    Update.doThisWhenCalled("Peter", 42);
  }  

}
export default Edit;

and later, in app.js I add a few Event handlers:

import Edit from "./Edit";
import Update from "./Update";

firstButton.addEventListener('click', Update.doThisAfterClick);

secondButton.addEventListener('click', Edit.fancyEventHandler); 

Now the crazy part: Clicking firstButton logged First button clicked! as expected, but clicking secondButton gave an error: Uncaught TypeError: Update.doThisWhenCalled is not a function..

I actually tried to debug this by inserting

let x = Update.doThisWhenCalled;
debugger;

into fancyEventHandler() and saw that x was undefined.

Through some sheer luck I saw that I could use

Update.default.doThisWhenCalled("Peter", 42);

instead and this resolved the issue. No idea why.

What is wrong with calling the static method directly? And what is this "default" property?