index.js
function setCookie (res, name, val, options) {
  var data = Cookie.serialize(name, val, options)

  var prev = res.getHeader('set-cookie') || []
  var header = Array.isArray(prev) ? prev.concat(data)
    : [prev, data]

  res.setHeader('set-cookie', header)
}
function setCookie (res, name, val, options) {
  var data = Cookie.serialize(name, val, options)

  var prev = res.getHeader('set-cookie') || []
  var header = Array.isArray(prev) ? prev.concat(data)
    : [prev, data]

  res.setHeader('set-cookie', header)
}
function setCookie ( res , name , val , options ) { var data = Cookie . serialize ( name , val , options ) var prev = res . getHeader ( 'set-cookie' ) || [ ] var header = Array . isArray ( prev ) ? prev . concat ( data ) : [ prev , data ] res . setHeader ( 'set-cookie' , header ) }
Set a cookie on the HTTP response.

@param {OutgoingMessage} res
@param {string} name
@param {string} val
@param {Object} [options]
@api private
Set a cookie on the HTTP response .