Res Append

{% include admonitions/note.html content="res.append() is supported by Express v4.11.0+" %} Appends the specified value to the HTTP response header field. If the header is not already set, it creates the header with the specified value. The value parameter can be a string or an array.

{% include admonitions/note.html content="calling res.set() after res.append() will reset the previously-set header value." %}

res.append('Link', ['<http://localhost/>', '<http://localhost:3000/>'])
res.append('Set-Cookie', 'foo=bar; Path=/; HttpOnly')
res.append('Warning', '199 Miscellaneous warning')