Unable to create / save a word document with OpenXml with angular / typescript / javascript

Question

I'm unable to create a document with Xml (OpenXml) in my angular - typescript application - file gets created but opened shows "found unreadable content in document..." error. When I open the file in notepad, all I see is the Xml.

let blob = new Blob([openXmlString)], {type: 'application/vnd.openxmlformats-officedocument.wordprocessingml.document'});
fileSaverService.save(blob, "Document.docx");

Using the same xml, I can create a document that actually works in C# using this code, trying to replicate this in my angular - typescript app

    using (var doc = WordprocessingDocument.FromFlatOpcString(openXmlString))
    {
        doc.SaveAs("Document.docx").Close();
    }

Could someone please let me know what I may be missing?

Thanks in advance.