代理请求
function Child () { Parent.call(this) }
function A (type) { return function B (option) { return function C (...args) {} } }
Object.keys(a).map((k) =>a[k])
前提:配置了 target 或 forward
content-length
to '0' if request is of DELETE type.x-forwarded-*
headers if specified in config.http/https.request
,并把请求的结构返回给原请求的 response
.