.doc files are pretty outdated, so do try other means if able to
.docx files are pretty much zipped files, which makes it harder to create than the older, standalone, .doc files. With .doc files, we can just go dive a bit into the code, study their syntax, then replicate it. With .docx files, it's like .doc files, but it's zipped with other components.
There were programs made for the creation of .docx files, but as of creating this, they're not really client-side friendly yet.