node.js - 在 Nodejs 中，当我 console.log 一个 req 对象时， [Circular] 引用了什么？如何确定

Question

在 Nodejs 中，当我 console.log 一个 req 对象时，[Circular] 是什么意思？

这是一个针对基本 nodejs 示例的 console.log(req) 示例。注意 request.socket._readWatcher.socket 是一个 [Circular]。这是否意味着它指的是自己？我怎样才能取消引用它？

{ socket: 
   { bufferSize: 0,
     fd: 7,
     type: 'tcp4',
     allowHalfOpen: true,
     _readWatcher: 
      { socket: [Circular],
        callback: [Function: onReadable] },
     destroyed: false,
     readable: true,
     _writeQueue: [],
     _writeQueueEncoding: [],
     _writeQueueFD: [],
     _writeQueueCallbacks: [],
     _writeWatcher: 
      { socket: [Circular],
        callback: [Function: onWritable] },
     writable: true,
     _writeImpl: [Function],
     _readImpl: [Function],
     _shutdownImpl: [Function],
     remoteAddress: '127.0.1.1',
     remotePort: 40407,
     server: 
      { connections: 1,
        allowHalfOpen: true,
        watcher: [Object],
        _events: [Object],
        httpAllowHalfOpen: false,
        type: 'tcp4',
        fd: 5 },
     ondrain: [Function],
     _idleTimeout: 120000,
     _idleNext: 
      { repeat: 120,
        _idleNext: [Circular],
        _idlePrev: [Circular],
        callback: [Function] },
     _idlePrev: 
      { repeat: 120,
        _idleNext: [Circular],
        _idlePrev: [Circular],
        callback: [Function] },
     _idleStart: Sun, 15 May 2011 01:18:50 GMT,
     _events: 
      { timeout: [Function],
        error: [Function],
        close: [Function] },
     ondata: [Function],
     onend: [Function],
     _httpMessage: 
      { output: [],
        outputEncodings: [],
        writable: true,
        _last: false,
        chunkedEncoding: true,
        shouldKeepAlive: true,
        useChunkedEncodingByDefault: true,
        _hasBody: true,
        _trailer: '',
        finished: false,
        socket: [Circular],
        connection: [Circular],
        _events: [Object],
        _header: 'HTTP/1.1 200 OK\r\nContent-Type: text/plain\r\nConnection: keep-alive\r\nTransfer-Encoding: chunked\r\n\r\n',
        _headerSent: false } },
  connection: 
   { bufferSize: 0,
     fd: 7,
     type: 'tcp4',
     allowHalfOpen: true,
     _readWatcher: 
      { socket: [Circular],
        callback: [Function: onReadable] },
     destroyed: false,
     readable: true,
     _writeQueue: [],
     _writeQueueEncoding: [],
     _writeQueueFD: [],
     _writeQueueCallbacks: [],
     _writeWatcher: 
      { socket: [Circular],
        callback: [Function: onWritable] },
     writable: true,
     _writeImpl: [Function],
     _readImpl: [Function],
     _shutdownImpl: [Function],
     remoteAddress: '127.0.1.1',
     remotePort: 40407,
     server: 
      { connections: 1,
        allowHalfOpen: true,
        watcher: [Object],
        _events: [Object],
        httpAllowHalfOpen: false,
        type: 'tcp4',
        fd: 5 },
     ondrain: [Function],
     _idleTimeout: 120000,
     _idleNext: 
      { repeat: 120,
        _idleNext: [Circular],
        _idlePrev: [Circular],
        callback: [Function] },
     _idlePrev: 
      { repeat: 120,
        _idleNext: [Circular],
        _idlePrev: [Circular],
        callback: [Function] },
     _idleStart: Sun, 15 May 2011 01:18:50 GMT,
     _events: 
      { timeout: [Function],
        error: [Function],
        close: [Function] },
     ondata: [Function],
     onend: [Function],
     _httpMessage: 
      { output: [],
        outputEncodings: [],
        writable: true,
        _last: false,
        chunkedEncoding: true,
        shouldKeepAlive: true,
        useChunkedEncodingByDefault: true,
        _hasBody: true,
        _trailer: '',
        finished: false,
        socket: [Circular],
        connection: [Circular],
        _events: [Object],
        _header: 'HTTP/1.1 200 OK\r\nContent-Type: text/plain\r\nConnection: keep-alive\r\nTransfer-Encoding: chunked\r\n\r\n',
        _headerSent: false } },
  httpVersion: '1.1',
  complete: false,
  headers: 
   { 'user-agent': 'curl/7.21.0 (x86_64-pc-linux-gnu) libcurl/7.21.0 OpenSSL/0.9.8o zlib/1.2.3.4 libidn/1.18',
     host: 'uh-uh-uh-I-aint-telling',
     accept: '*/*' },
  trailers: {},
  readable: true,
  url: '/',
  method: 'GET',
  statusCode: null,
  client: 
   { bufferSize: 0,
     fd: 7,
     type: 'tcp4',
     allowHalfOpen: true,
     _readWatcher: 
      { socket: [Circular],
        callback: [Function: onReadable] },
     destroyed: false,
     readable: true,
     _writeQueue: [],
     _writeQueueEncoding: [],
     _writeQueueFD: [],
     _writeQueueCallbacks: [],
     _writeWatcher: 
      { socket: [Circular],
        callback: [Function: onWritable] },
     writable: true,
     _writeImpl: [Function],
     _readImpl: [Function],
     _shutdownImpl: [Function],
     remoteAddress: '127.0.1.1',
     remotePort: 40407,
     server: 
      { connections: 1,
        allowHalfOpen: true,
        watcher: [Object],
        _events: [Object],
        httpAllowHalfOpen: false,
        type: 'tcp4',
        fd: 5 },
     ondrain: [Function],
     _idleTimeout: 120000,
     _idleNext: 
      { repeat: 120,
        _idleNext: [Circular],
        _idlePrev: [Circular],
        callback: [Function] },
     _idlePrev: 
      { repeat: 120,
        _idleNext: [Circular],
        _idlePrev: [Circular],
        callback: [Function] },
     _idleStart: Sun, 15 May 2011 01:18:50 GMT,
     _events: 
      { timeout: [Function],
        error: [Function],
        close: [Function] },
     ondata: [Function],
     onend: [Function],
     _httpMessage: 
      { output: [],
        outputEncodings: [],
        writable: true,
        _last: false,
        chunkedEncoding: true,
        shouldKeepAlive: true,
        useChunkedEncodingByDefault: true,
        _hasBody: true,
        _trailer: '',
        finished: false,
        socket: [Circular],
        connection: [Circular],
        _events: [Object],
        _header: 'HTTP/1.1 200 OK\r\nContent-Type: text/plain\r\nConnection: keep-alive\r\nTransfer-Encoding: chunked\r\n\r\n',
        _headerSent: false } },
  httpVersionMajor: 1,
  httpVersionMinor: 1,
  upgrade: false }

更新

由于我显然没有尽可能清楚，我如何才能取消引用循环引用的元素？它总是父元素吗？

另外值得注意的是，昨晚我了解了 Utils 类和检查方法。这可能会给我提供比我合理地想知道的更多的信息；)

Answer 1

这是一个循环引用。就是这样。

示例:

a.b = a

现在记录一下:

[Object a] {
    b: [Object a] {
        b: [Object a] {
            b: [Object a] {
                b: [Object a] {
                    b: [Object a] {
                        b: [Object a] {
                            ... welcome to recursion!
                        }
                    }
                }

            }
        }
    }
}

它永远不会结束，log 调用会产生堆栈溢出，仅此而已。 Node 检测到这些并给出循环引用文本。