_includes/api/en/3x/req-accepts.md
Check if the given types are acceptable, returning
the best match when true, otherwise undefined - in which
case you should respond with 406 "Not Acceptable".
The type value may be a single mime type string
such as "application/json", the extension name
such as "json", a comma-delimited list or an array. When a list
or array is given the best match, if any is returned.
// Accept: text/html
req.accepts('html')
// => "html"
// Accept: text/*, application/json
req.accepts('html')
// => "html"
req.accepts('text/html')
// => "text/html"
req.accepts('json, text')
// => "json"
req.accepts('application/json')
// => "application/json"
// Accept: text/*, application/json
req.accepts('image/png')
req.accepts('png')
// => undefined
// Accept: text/*;q=.5, application/json
req.accepts(['html', 'json'])
req.accepts('html, json')
// => "json"