CommonJS JavaScript modules – passing data to parent functions

Using CommonJS JavaScript Modules.
I have a module that I cannot edit or control. I call this the parent module.

I want to build on the parent’s functionality with additional features. Some of these child features need to use the functions in the parent. So I need to pass data to the parent and have it run like it was part of the parent module. The whole of the parent is exported.

Parent

function ParentModule () {
  DefaultElement.setStatus = function (status, block) {
    var statusBlock = block.querySelector('.' + this.statusBlock)
    var statusText = status ? 'Available' : 'Out of Stock';
  
    statusBlock.innerHTML = statusText;
  }
}

Child

function ChildModule () {
  UpdatedElement.update = function (el) {
    var selected = document.getElementById(el)
    var block = this.getBlock(selected)

    window.ParentModule.DefaultElement.setStatus(true, block);
  }
}

(Expected) Error

Uncaught TypeError: Cannot set properties of null (setting 'innerHTML')

What is the syntax or pattern for this?

Calling the relevant function within the child module, simply causes an error. As I understand this is expected – as the child module imports the parent function it runs within the child so doesn’t have access to the same data.

Rather than import into the child is there a way to have the child module simple behave like it was all one file? Or how can I pass data up to the parent and have it behave like it’s always been part of the parent?