How to Open a DOCX File into the Current Document Using OfficeJS

Question

Hi there,

I'm developing a Word Add-in (Taskpane) which the main goal is replace some predefined content controls of documents persisted in a database. This add-in is a web app using Office.JS. Based on some user input the Add-in get the file and open it.

My first approach based in documentation (office) was the following:

fetch(`/arquivo?id=${idModeloDocumento}`)  
        .then(response => response.text())  
        .then(base64String => {  
  
            Word.run(async context => {  
                const app = context.application;   
                const doc = app.createDocument(base64String); // base64string comes from my backend app  
                doc.open();  
                await context.sync();  
            });  
        })  

However, it opens the document on a new instance of Word. That's not comfortable to our users.
First Question: Is there a method to open it in the current document object?

So, as a workaround I didn't open the document. After createDocument method calling, I got body and header Ooxml and inserted into the current document instead.
Like this:

fetch(`/arquivo?id=${idModeloDocumento}`)  
        .then(response => response.text())  
        .then(base64String => {  
  
           Word.run(async context => {  
                var base64doc = base64String  
                const app = context.application  
                const doc = app.createDocument(base64doc)  
                await context.sync()  
                console.log("Novo documento criado")  
  
                let bodyOoxml = doc.body.getOoxml()  
                let headerOoxml = doc.sections.getFirst().getHeader(Word.HeaderFooterType.primary).getOoxml()  
  
                await context.sync()  
                console.log("Preenchendo o body do documento corrente")  
  
                let curHeader = context.document.sections.getFirst().getHeader(Word.HeaderFooterType.primary)  
                curHeader.insertOoxml(headerOoxml.value, Word.InsertLocation.replace)  
  
                let curBody = context.document.body  
                curBody.insertOoxml(bodyOoxml.value, Word.InsertLocation.replace)  
  
                await context.sync()  
                console.log("Pronto")  
            });                          
              
        })  

It worked, but I'm not 100% sure that's the correct way to do that.
Can you help me? Can you drive me to a documentation or samples where I can learn how to deal with this kind of situation the right way?

Regards,
Marco