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。

根据zainengineer的回答…另一种方法是对对象进行深度复制，去掉循环引用并对结果进行字符串化。

function cleanStringify(object) { if (object && typeof object === 'object') { object = copyWithoutCircularReferences([object], object); } return JSON.stringify(object); function copyWithoutCircularReferences(references, object) { var cleanObject = {}; Object.keys(object).forEach(function(key) { var value = object[key]; if (value && typeof value === 'object') { if (references.indexOf(value) < 0) { references.push(value); cleanObject[key] = copyWithoutCircularReferences(references, value); references.pop(); } else { cleanObject[key] = '###_Circular_###'; } } else if (typeof value !== 'function') { cleanObject[key] = value; } }); return cleanObject; } } // Example var a = { name: "a" }; var b = { name: "b" }; b.a = a; a.b = b; console.log(cleanStringify(a)); console.log(cleanStringify(b));

一种方法是从主对象中剥离对象和函数。并对更简单的形式进行stringalize

function simpleStringify (object){
    // stringify an object, avoiding circular structures
    // https://stackoverflow.com/a/31557814
    var simpleObject = {};
    for (var prop in object ){
        if (!object.hasOwnProperty(prop)){
            continue;
        }
        if (typeof(object[prop]) == 'object'){
            continue;
        }
        if (typeof(object[prop]) == 'function'){
            continue;
        }
        simpleObject[prop] = object[prop];
    }
    return JSON.stringify(simpleObject); // returns cleaned up JSON
};

如果你使用node js使用inspect()(参考文档)

import {inspect} from "util";
console.log(inspect(object));

根据MDN: https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/JSON/stringify#issue_with_json.stringify_when_serializing_circular_references

它是一个循环json，不能直接转换。

解决方案1:

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

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

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

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

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

解决方案2:(同样通过MDN)

https://github.com/douglascrockford/JSON-js

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