I have a working solution for reading and writing excel files. But I am trying to figure out how to send an object from/to the same files?

I have been trying to send an object over to another file. I have the solution for writing to an excel file by pushing a button on the frontend, and the file gets written on the backend.

However, I am tring to do something similar, only I want to be able to send an object that would be contained on the button page, over the file (post.controllers). But anything I try doesn't work. Can I have some suggestions please? Here is the link to the files on Github. There are no node modules, because I was having errors uploading/pushing 

 https://github.com/ThomasM10/01WorkingExcelEdit-Test02

What I have tried:

I have tried many things, one such as 

// in the buttonPage.  

<pre>const objectTransfer = (event) => {
    event.preventDefault();
    fetch("http://localhost:3000/storedReceivingObject", {
        method: 'POST',
        body: JSON.stringify(storedReceivingObject),
        headers: {
        'Accept': 'application/json',
        },
    }
)}

app.use('/storedReceivingObject', postRoutes);