在我的例子中，它是在一些代码更改后留在单元测试中的flush()。

之前

it('something should be...', () => {
// do tests
flush();
}

后

it('something should be...', () => {
// do tests
}

在尝试用jQuery构建下面的消息时，我也遇到过同样的错误。循环引用发生在reviewerName被错误地分配给msg.detail.reviewerName时。JQuery的.val()修复了这个问题，参见最后一行。

var reviewerName = $('reviewerName'); // <input type="text" id="taskName" />;
var msg = {"type":"A", "detail":{"managerReview":true} };
msg.detail.reviewerName = reviewerName; // Error
msg.detail.reviewerName = reviewerName.val(); // Fixed

根据Mozilla的JSON文档，JSON。Stringify有第二个参数替换器，可以用来在解析树时过滤/忽略子项。然而，也许您可以避免循环引用。

在Node.js中我们不能。所以我们可以这样做:

function censor(censor) {
  var i = 0;
  
  return function(key, value) {
    if(i !== 0 && typeof(censor) === 'object' && typeof(value) == 'object' && censor == value) 
      return '[Circular]'; 
    
    if(i >= 29) // seems to be a harded maximum of 30 serialized objects?
      return '[Unknown]';
    
    ++i; // so we know we aren't using the original object anymore
    
    return value;  
  }
}

var b = {foo: {bar: null}};

b.foo.bar = b;

console.log("Censoring: ", b);

console.log("Result: ", JSON.stringify(b, censor(b)));

结果:

Censoring:  { foo: { bar: [Circular] } }
Result: {"foo":{"bar":"[Circular]"}}

不幸的是，在自动假设它是循环之前，它似乎最多迭代了30次。否则，这应该可以工作。我甚至在这里使用了areEquivalent, JSON。Stringify在30次迭代之后仍然抛出异常。尽管如此，如果您确实需要的话，在顶层获得对象的体面表示已经足够好了。也许有人可以改进一下?在Node.js的HTTP请求对象，我得到:

{
"limit": null,
"size": 0,
"chunks": [],
"writable": true,
"readable": false,
"_events": {
    "pipe": [null, null],
    "error": [null]
},
"before": [null],
"after": [],
"response": {
    "output": [],
    "outputEncodings": [],
    "writable": true,
    "_last": false,
    "chunkedEncoding": false,
    "shouldKeepAlive": true,
    "useChunkedEncodingByDefault": true,
    "_hasBody": true,
    "_trailer": "",
    "finished": false,
    "socket": {
        "_handle": {
            "writeQueueSize": 0,
            "socket": "[Unknown]",
            "onread": "[Unknown]"
        },
        "_pendingWriteReqs": "[Unknown]",
        "_flags": "[Unknown]",
        "_connectQueueSize": "[Unknown]",
        "destroyed": "[Unknown]",
        "bytesRead": "[Unknown]",
        "bytesWritten": "[Unknown]",
        "allowHalfOpen": "[Unknown]",
        "writable": "[Unknown]",
        "readable": "[Unknown]",
        "server": "[Unknown]",
        "ondrain": "[Unknown]",
        "_idleTimeout": "[Unknown]",
        "_idleNext": "[Unknown]",
        "_idlePrev": "[Unknown]",
        "_idleStart": "[Unknown]",
        "_events": "[Unknown]",
        "ondata": "[Unknown]",
        "onend": "[Unknown]",
        "_httpMessage": "[Unknown]"
    },
    "connection": "[Unknown]",
    "_events": "[Unknown]",
    "_headers": "[Unknown]",
    "_headerNames": "[Unknown]",
    "_pipeCount": "[Unknown]"
},
"headers": "[Unknown]",
"target": "[Unknown]",
"_pipeCount": "[Unknown]",
"method": "[Unknown]",
"url": "[Unknown]",
"query": "[Unknown]",
"ended": "[Unknown]"
}

我创建了一个小的Node.js模块来做这件事:https://github.com/ericmuyser/stringy欢迎改进/贡献!

我通常使用circular-json npm包来解决这个问题。

// Felix Kling's example
var a = {};
a.b = a;
// load circular-json module
var CircularJSON = require('circular-json');
console.log(CircularJSON.stringify(a));
//result
{"b":"~"}

注意:CircularJSON已弃用，我现在使用flatted(来自CircularJSON的创建者):

// ESM
import {parse, stringify} from 'flatted/esm';

// CJS
const {parse, stringify} = require('flatted/cjs');

const a = [{}];
a[0].a = a;
a.push(a);

stringify(a); // [["1","0"],{"a":"0"}]

来自:https://www.npmjs.com/package/flatted

这可以工作并告诉您哪些属性是循环的。它还允许使用引用重新构造对象

  JSON.stringifyWithCircularRefs = (function() {
    const refs = new Map();
    const parents = [];
    const path = ["this"];

    function clear() {
      refs.clear();
      parents.length = 0;
      path.length = 1;
    }

    function updateParents(key, value) {
      var idx = parents.length - 1;
      var prev = parents[idx];
      if (prev[key] === value || idx === 0) {
        path.push(key);
        parents.push(value);
      } else {
        while (idx-- >= 0) {
          prev = parents[idx];
          if (prev[key] === value) {
            idx += 2;
            parents.length = idx;
            path.length = idx;
            --idx;
            parents[idx] = value;
            path[idx] = key;
            break;
          }
        }
      }
    }

    function checkCircular(key, value) {
      if (value != null) {
        if (typeof value === "object") {
          if (key) { updateParents(key, value); }

          let other = refs.get(value);
          if (other) {
            return '[Circular Reference]' + other;
          } else {
            refs.set(value, path.join('.'));
          }
        }
      }
      return value;
    }

    return function stringifyWithCircularRefs(obj, space) {
      try {
        parents.push(obj);
        return JSON.stringify(obj, checkCircular, space);
      } finally {
        clear();
      }
    }
  })();

删除大量噪音的例子:

{
    "requestStartTime": "2020-05-22...",
    "ws": {
        "_events": {},
        "readyState": 2,
        "_closeTimer": {
            "_idleTimeout": 30000,
            "_idlePrev": {
                "_idleNext": "[Circular Reference]this.ws._closeTimer",
                "_idlePrev": "[Circular Reference]this.ws._closeTimer",
                "expiry": 33764,
                "id": -9007199254740987,
                "msecs": 30000,
                "priorityQueuePosition": 2
            },
            "_idleNext": "[Circular Reference]this.ws._closeTimer._idlePrev",
            "_idleStart": 3764,
            "_destroyed": false
        },
        "_closeCode": 1006,
        "_extensions": {},
        "_receiver": {
            "_binaryType": "nodebuffer",
            "_extensions": "[Circular Reference]this.ws._extensions",
        },
        "_sender": {
            "_extensions": "[Circular Reference]this.ws._extensions",
            "_socket": {
                "_tlsOptions": {
                    "pipe": false,
                    "secureContext": {
                        "context": {},
                        "singleUse": true
                    },
                },
                "ssl": {
                    "_parent": {
                        "reading": true
                    },
                    "_secureContext": "[Circular Reference]this.ws._sender._socket._tlsOptions.secureContext",
                    "reading": true
                }
            },
            "_firstFragment": true,
            "_compress": false,
            "_bufferedBytes": 0,
            "_deflating": false,
            "_queue": []
        },
        "_socket": "[Circular Reference]this.ws._sender._socket"
    }
}

为了重建调用JSON.parse()，然后遍历属性寻找[Circular Reference]标记。然后把它切下来…eval……它将此设置为根对象。

不要评估任何可能被黑的东西。更好的做法是执行string.split('.')，然后按名称查找属性来设置引用。

这意味着你在请求中传递的对象(我猜是pagedoc)有一个循环引用，类似于:

var a = {};
a.b = a;

JSON。Stringify不能像这样转换结构。

注意:这将是DOM节点的情况，它们具有循环引用，即使它们没有附加到DOM树。每个节点都有一个ownerDocument，它在大多数情况下引用document。document至少通过document有一个对DOM树的引用。body和document.body. ownerdocument再次指向document，而document只是DOM树中多个循环引用中的一个。