Remove HTML document elements from JS embed?

Hi,

I've created a form and want to embed it using JS. However, the JS snippet seems to include HTML document elements:

document.write(""+"\n");
document.write("<html lang="en">"+"\n");
document.write(""+"\n");
document.write(" <meta charset="UTF-8" />"+"\n");
document.write(" <meta name="viewport" content="width=device-width, initial-scale=1">"+"\n");

This makes it difficult for me to embed the form in the middle of an existing page.

How do I remove these HTML document elements?

Thanks!