Why value cannot be sent as an HTTP header value, or undefined when it can. Node
throws an opaque "Invalid character in header content" at request time for a CR/LF
(or any other C0 control or DEL) and for any character above U+00FF; a blank value
would send an empty header. Tab is allowed, as in HTTP. Shared by the engine
(userAgent) and the CLI's --user-agent parser. Checked by char code so the
source stays free of control bytes.
Why
valuecannot be sent as an HTTP header value, or undefined when it can. Node throws an opaque "Invalid character in header content" at request time for a CR/LF (or any other C0 control or DEL) and for any character above U+00FF; a blank value would send an empty header. Tab is allowed, as in HTTP. Shared by the engine (userAgent) and the CLI's--user-agentparser. Checked by char code so the source stays free of control bytes.