鉴于我在大型 JavaScript 对象中有循环引用
我试试JSON.stringify(problematicObject)
浏览器抛出
“TypeError：将循环结构转换为 JSON”
（这是预期的）
那我想找这个循环引用的原因，最好用Chrome开发者工具？这可能吗？如何在大对象中查找和修复循环引用？
【问题讨论】：
problematicObject是什么吗？
JSON.stringify(window); 是导致该错误的一种情况。
{} 创建的，或原生函数之一），还是宿主对象（例如，DOM 元素）？
标签： javascript
大多数其他答案仅显示如何检测对象树具有循环引用——它们没有告诉您如何修复这些循环引用（即将循环引用值替换为 undefined）。
下面是我用undefined替换所有循环引用的函数：
export const specialTypeHandlers_default = [
// Set and Map are included by default, since JSON.stringify tries (and fails) to serialize them by default
{type: Set, keys: a=>a.keys(), get: (a, key)=>key, delete: (a, key)=>a.delete(key)},
{type: Map, keys: a=>a.keys(), get: (a, key)=>a.get(key), delete: (a, key)=>a.set(key, undefined)},
];
export function RemoveCircularLinks(node, specialTypeHandlers = specialTypeHandlers_default, nodeStack_set = new Set()) {
nodeStack_set.add(node);
const specialHandler = specialTypeHandlers.find(a=>node instanceof a.type);
for (const key of specialHandler ? specialHandler.keys(node) : Object.keys(node)) {
const value = specialHandler ? specialHandler.get(node, key) : node[key];
// if the value is already part of visited-stack, delete the value (and don't tunnel into it)
if (nodeStack_set.has(value)) {
if (specialHandler) specialHandler.delete(node, key);
else node[key] = undefined;
}
// else, tunnel into it, looking for circular-links at deeper levels
else if (typeof value == "object" && value != null) {
RemoveCircularLinks(value, specialTypeHandlers, nodeStack_set);
}
}
nodeStack_set.delete(node);
}
特别是与JSON.stringify一起使用，只需在字符串化之前调用上面的函数（注意它确实改变了传入的对象）：
const objTree = {normalProp: true};
objTree.selfReference = objTree;
RemoveCircularLinks(objTree); // without this line, the JSON.stringify call errors
console.log(JSON.stringify(objTree));
【讨论】：
这是我的 CircularReferenceDetector 类，它输出循环引用值实际所在的所有属性堆栈信息，并显示罪魁祸首引用的位置。
这对于大型结构特别有用，因为通过键无法明显看出哪个值是伤害的来源。
它输出字符串化的循环引用值，但所有对自身的引用都替换为“[Circular object --- fix me]”。
用法：
CircularReferenceDetector.detectCircularReferences(value);
注意： 如果您不想使用任何日志记录或没有可用的记录器，请删除 Logger.* 语句。
技术说明：
递归函数遍历对象的所有属性并测试 JSON.stringify 是否成功。
如果它不成功（循环引用），那么它通过用一些常量字符串替换 value 本身来测试它是否成功。这意味着如果它成功使用这个替换器，这个值就是循环引用的值。如果不是，则递归遍历该对象的所有属性。
同时它还跟踪属性堆栈，为您提供罪魁祸首值所在的信息。
import {Logger} from "../Logger";
export class CircularReferenceDetector {
static detectCircularReferences(toBeStringifiedValue: any, serializationKeyStack: string[] = []) {
Object.keys(toBeStringifiedValue).forEach(key => {
var value = toBeStringifiedValue[key];
var serializationKeyStackWithNewKey = serializationKeyStack.slice();
serializationKeyStackWithNewKey.push(key);
try {
JSON.stringify(value);
Logger.debug(`path "${Util.joinStrings(serializationKeyStack)}" is ok`);
} catch (error) {
Logger.debug(`path "${Util.joinStrings(serializationKeyStack)}" JSON.stringify results in error: ${error}`);
var isCircularValue:boolean;
var circularExcludingStringifyResult:string = "";
try {
circularExcludingStringifyResult = JSON.stringify(value, CircularReferenceDetector.replaceRootStringifyReplacer(value), 2);
isCircularValue = true;
} catch (error) {
Logger.debug(`path "${Util.joinStrings(serializationKeyStack)}" is not the circular source`);
CircularReferenceDetector.detectCircularReferences(value, serializationKeyStackWithNewKey);
isCircularValue = false;
}
if (isCircularValue) {
throw new Error(`Circular reference detected:\nCircularly referenced value is value under path "${Util.joinStrings(serializationKeyStackWithNewKey)}" of the given root object\n`+
`Calling stringify on this value but replacing itself with [Circular object --- fix me] ( <-- search for this string) results in:\n${circularExcludingStringifyResult}\n`);
}
}
});
}
private static replaceRootStringifyReplacer(toBeStringifiedValue: any): any {
var serializedObjectCounter = 0;
return function (key: any, value: any) {
if (serializedObjectCounter !== 0 && typeof(toBeStringifiedValue) === 'object' && toBeStringifiedValue === value) {
Logger.error(`object serialization with key ${key} has circular reference to being stringified object`);
return '[Circular object --- fix me]';
}
serializedObjectCounter++;
return value;
}
}
}
export class Util {
static joinStrings(arr: string[], separator: string = ":") {
if (arr.length === 0) return "";
return arr.reduce((v1, v2) => `${v1}${separator}${v2}`);
}
}
"use strict";
const Logger_1 = require("../Logger");
class CircularReferenceDetector {
static detectCircularReferences(toBeStringifiedValue, serializationKeyStack = []) {
Object.keys(toBeStringifiedValue).forEach(key => {
var value = toBeStringifiedValue[key];
var serializationKeyStackWithNewKey = serializationKeyStack.slice();
serializationKeyStackWithNewKey.push(key);
try {
JSON.stringify(value);
Logger_1.Logger.debug(`path "${Util.joinStrings(serializationKeyStack)}" is ok`);
}
catch (error) {
Logger_1.Logger.debug(`path "${Util.joinStrings(serializationKeyStack)}" JSON.stringify results in error: ${error}`);
var isCircularValue;
var circularExcludingStringifyResult = "";
try {
circularExcludingStringifyResult = JSON.stringify(value, CircularReferenceDetector.replaceRootStringifyReplacer(value), 2);
isCircularValue = true;
}
catch (error) {
Logger_1.Logger.debug(`path "${Util.joinStrings(serializationKeyStack)}" is not the circular source`);
CircularReferenceDetector.detectCircularReferences(value, serializationKeyStackWithNewKey);
isCircularValue = false;
}
if (isCircularValue) {
throw new Error(`Circular reference detected:\nCircularly referenced value is value under path "${Util.joinStrings(serializationKeyStackWithNewKey)}" of the given root object\n` +
`Calling stringify on this value but replacing itself with [Circular object --- fix me] ( <-- search for this string) results in:\n${circularExcludingStringifyResult}\n`);
}
}
});
}
static replaceRootStringifyReplacer(toBeStringifiedValue) {
var serializedObjectCounter = 0;
return function (key, value) {
if (serializedObjectCounter !== 0 && typeof (toBeStringifiedValue) === 'object' && toBeStringifiedValue === value) {
Logger_1.Logger.error(`object serialization with key ${key} has circular reference to being stringified object`);
return '[Circular object --- fix me]';
}
serializedObjectCounter++;
return value;
};
}
}
exports.CircularReferenceDetector = CircularReferenceDetector;
class Util {
static joinStrings(arr, separator = ":") {
if (arr.length === 0)
return "";
return arr.reduce((v1, v2) => `${v1}${separator}${v2}`);
}
}
exports.Util = Util;
【讨论】：
您也可以使用符号 - 由于这种方法，您不必改变原始对象的属性，除了添加符号来标记访问的节点。
它更干净，应该比收集节点属性和与对象比较更快。如果您不想序列化大的嵌套值，它还具有可选的深度限制：
// Symbol used to mark already visited nodes - helps with circular dependencies
const visitedMark = Symbol('VISITED_MARK');
const MAX_CLEANUP_DEPTH = 10;
function removeCirculars(obj, depth = 0) {
if (!obj) {
return obj;
}
// Skip condition - either object is falsy, was visited or we go too deep
const shouldSkip = !obj || obj[visitedMark] || depth > MAX_CLEANUP_DEPTH;
// Copy object (we copy properties from it and mark visited nodes)
const originalObj = obj;
let result = {};
Object.keys(originalObj).forEach((entry) => {
const val = originalObj[entry];
if (!shouldSkip) {
if (typeof val === 'object') { // Value is an object - run object sanitizer
originalObj[visitedMark] = true; // Mark current node as "seen" - will stop from going deeper into circulars
const nextDepth = depth + 1;
result[entry] = removeCirculars(val, nextDepth);
} else {
result[entry] = val;
}
} else {
result = 'CIRCULAR';
}
});
return result;
}
这将导致对象的所有循环依赖项被剥离，并且不会比给定的MAX_CLEANUP_DEPTH 更深。
只要您不对对象执行任何元编程操作，使用符号是安全的 - 它们是透明的且不可枚举，因此 - 它们不会显示在对象的任何标准操作中。
此外，如果您需要对其执行任何其他操作，返回一个新的、已清理的对象具有不会改变原始对象的优点。
如果您不想标记CIRCULAR，您可以稍微修改一下代码，从而在实际执行操作之前跳过对象（在循环内）：
originalObj[visitedMark] = true; // Mark current node as "seen" - will stop from going deeper into circulars
const val = originalObj[entry];
// Skip condition - either object is falsy, was visited or we go too deep
const shouldSkip = val[visitedMark] || depth > MAX_SANITIZATION_DEPTH;
if (!shouldSkip) {
if (typeof val === 'object') { // Value is an object - run object sanitizer
const nextDepth = depth + 1;
result[entry] = removeCirculars(val, nextDepth);
} else {
result[entry] = val;
}
}
【讨论】：
以下是 MDN 在循环对象上使用 JSON.stringify() 时检测和修复循环引用的方法：https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Errors/Cyclic_object_value：
像下面这样的循环结构
var circularReference = {otherData: 123};
circularReference.myself = circularReference;
JSON.stringify()将失败：
JSON.stringify(circularReference);
// TypeError: cyclic object value
要序列化循环引用，您可以使用支持它们的库（例如cycle.js）或自行实施解决方案，这需要通过可序列化值查找和替换（或删除）循环引用。
下面的 sn-p 说明了如何使用 the replacer parameter of
JSON.stringify()查找和过滤（从而导致数据丢失）循环引用：
const getCircularReplacer = () => {
const seen = new WeakSet();
return (key, value) => {
if (typeof value === "object" && value !== null) {
if (seen.has(value)) {
return;
}
seen.add(value);
}
return value;
};
};
JSON.stringify(circularReference, getCircularReplacer());
// {"otherData":123}
【讨论】：
只是为了把我的版本混在一起...下面是 @dkurzaj 's code 的混音（它本身是 @Aaron V 的混音，@user4976005 的混音，@Trey Mack 的混音，最后是 @Freddie Nfbnm的 [已删除？] 代码）加上 @darksinge 's WeakMap idea。所以……我猜这个帖子是 Megamix :)
在我的版本中，可以选择将报告（而不是console.log'ed 条目）作为对象数组返回。如果不需要报告，则在第一次看到循环引用（a'la @darksinge 的代码）时停止测试。
此外，hasOwnProperty 已被删除，因为 Object.keys 仅返回 hasOwnProperty 属性（请参阅：https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Object/keys）。
function isCyclic(x, bReturnReport) {
var a_sKeys = [],
a_oStack = [],
wm_oSeenObjects = new WeakMap(), //# see: https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/WeakMap
oReturnVal = {
found: false,
report: []
}
;
//# Setup the recursive logic to locate any circular references while kicking off the initial call
(function doIsCyclic(oTarget, sKey) {
var a_sTargetKeys, sCurrentKey, i;
//# If we've seen this oTarget before, flip our .found to true
if (wm_oSeenObjects.has(oTarget)) {
oReturnVal.found = true;
//# If we are to bReturnReport, add the entries into our .report
if (bReturnReport) {
oReturnVal.report.push({
instance: oTarget,
source: a_sKeys.slice(0, a_oStack.indexOf(oTarget) + 1).join('.'),
duplicate: a_sKeys.join('.') + "." + sKey
});
}
}
//# Else if oTarget is an instanceof Object, determine the a_sTargetKeys and .set our oTarget into the wm_oSeenObjects
else if (oTarget instanceof Object) {
a_sTargetKeys = Object.keys(oTarget);
wm_oSeenObjects.set(oTarget /*, undefined*/);
//# If we are to bReturnReport, .push the current level's/call's items onto our stacks
if (bReturnReport) {
if (sKey) { a_sKeys.push(sKey) };
a_oStack.push(oTarget);
}
//# Traverse the a_sTargetKeys, pulling each into sCurrentKey as we go
//# NOTE: If you want all properties, even non-enumerables, see Object.getOwnPropertyNames() so there is no need to call .hasOwnProperty (per: https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Object/keys)
for (i = 0; i < a_sTargetKeys.length; i++) {
sCurrentKey = a_sTargetKeys[i];
//# If we've already .found a circular reference and we're not bReturnReport, fall from the loop
if (oReturnVal.found && !bReturnReport) {
break;
}
//# Else if the sCurrentKey is an instanceof Object, recurse to test
else if (oTarget[sCurrentKey] instanceof Object) {
doIsCyclic(oTarget[sCurrentKey], sCurrentKey);
}
}
//# .delete our oTarget into the wm_oSeenObjects
wm_oSeenObjects.delete(oTarget);
//# If we are to bReturnReport, .pop the current level's/call's items off our stacks
if (bReturnReport) {
if (sKey) { a_sKeys.pop() };
a_oStack.pop();
}
}
}(x, '')); //# doIsCyclic
return (bReturnReport ? oReturnVal.report : oReturnVal.found);
}
【讨论】：
这里有很多答案，但我想我会将我的解决方案添加到组合中。它类似于@Trey Mack 的答案，但该解决方案需要 O(n^2)。此版本使用WeakMap 代替数组，将时间缩短到 O(n)。
function isCyclic(object) {
const seenObjects = new WeakMap(); // use to keep track of which objects have been seen.
function detectCycle(obj) {
// If 'obj' is an actual object (i.e., has the form of '{}'), check
// if it's been seen already.
if (Object.prototype.toString.call(obj) == '[object Object]') {
if (seenObjects.has(obj)) {
return true;
}
// If 'obj' hasn't been seen, add it to 'seenObjects'.
// Since 'obj' is used as a key, the value of 'seenObjects[obj]'
// is irrelevent and can be set as literally anything you want. I
// just went with 'undefined'.
seenObjects.set(obj, undefined);
// Recurse through the object, looking for more circular references.
for (var key in obj) {
if (detectCycle(obj[key])) {
return true;
}
}
// If 'obj' is an array, check if any of it's elements are
// an object that has been seen already.
} else if (Array.isArray(obj)) {
for (var i in obj) {
if (detectCycle(obj[i])) {
return true;
}
}
}
return false;
}
return detectCycle(object);
}
这就是它在行动中的样子。
> var foo = {grault: {}};
> detectCycle(foo);
false
> foo.grault = foo;
> detectCycle(foo);
true
> var bar = {};
> detectCycle(bar);
false
> bar.plugh = [];
> bar.plugh.push(bar);
> detectCycle(bar);
true
【讨论】：
@tmack 的答案绝对是我发现这个问题时所寻找的！
不幸的是，它会返回许多误报 - 如果在 JSON 中复制对象，它会返回 true，这与循环性不同。循环性意味着一个对象是它自己的孩子，例如
obj.key1.key2.[...].keyX === obj
我修改了原始答案，这对我有用：
function isCyclic(obj) {
var keys = [];
var stack = [];
var stackSet = new Set();
var detected = false;
function detect(obj, key) {
if (obj && typeof obj != 'object') { return; }
if (stackSet.has(obj)) { // it's cyclic! Print the object and its locations.
var oldindex = stack.indexOf(obj);
var l1 = keys.join('.') + '.' + key;
var l2 = keys.slice(0, oldindex + 1).join('.');
console.log('CIRCULAR: ' + l1 + ' = ' + l2 + ' = ' + obj);
console.log(obj);
detected = true;
return;
}
keys.push(key);
stack.push(obj);
stackSet.add(obj);
for (var k in obj) { //dive on the object's children
if (Object.prototype.hasOwnProperty.call(obj, k)) { detect(obj[k], k); }
}
keys.pop();
stack.pop();
stackSet.delete(obj);
return;
}
detect(obj, 'obj');
return detected;
}
这里有一些非常简单的测试：
var root = {}
var leaf = {'isleaf':true};
var cycle2 = {l:leaf};
var cycle1 = {c2: cycle2, l:leaf};
cycle2.c1 = cycle1
root.leaf = leaf
isCyclic(cycle1); // returns true, logs "CIRCULAR: obj.c2.c1 = obj"
isCyclic(cycle2); // returns true, logs "CIRCULAR: obj.c1.c2 = obj"
isCyclic(leaf); // returns false
isCyclic(root); // returns false
【讨论】：
if (typeof obj != 'object') { return; } 应该是 if (obj && typeof obj != 'object') { return; } 因为typeof null == "object"。
这是由@Aaron V 和@user4976005 的答案混合而成的Node ES6 版本，它解决了调用hasOwnProperty 的问题：
const isCyclic = (obj => {
const keys = []
const stack = []
const stackSet = new Set()
let detected = false
const detect = ((object, key) => {
if (!(object instanceof Object))
return
if (stackSet.has(object)) { // it's cyclic! Print the object and its locations.
const oldindex = stack.indexOf(object)
const l1 = `${keys.join('.')}.${key}`
const l2 = keys.slice(0, oldindex + 1).join('.')
console.log(`CIRCULAR: ${l1} = ${l2} = ${object}`)
console.log(object)
detected = true
return
}
keys.push(key)
stack.push(object)
stackSet.add(object)
Object.keys(object).forEach(k => { // dive on the object's children
if (k && Object.prototype.hasOwnProperty.call(object, k))
detect(object[k], k)
})
keys.pop()
stack.pop()
stackSet.delete(object)
})
detect(obj, 'obj')
return detected
})
【讨论】：
你也可以将JSON.stringify与try/catch一起使用
function hasCircularDependency(obj)
{
try
{
JSON.stringify(obj);
}
catch(e)
{
return e.includes("Converting circular structure to JSON");
}
return false;
}
演示
function hasCircularDependency(obj) {
try {
JSON.stringify(obj);
} catch (e) {
return String(e).includes("Converting circular structure to JSON");
}
return false;
}
var a = {b:{c:{d:""}}};
console.log(hasCircularDependency(a));
a.b.c.d = a;
console.log(hasCircularDependency(a));【讨论】：
I want to find the **cause** of this circular reference 中说（强调我的）。所以你的回答根本不回答OP的问题。
我将 Freddie Nfbnm 的答案转换为 TypeScript：
export class JsonUtil {
static isCyclic(json) {
const keys = [];
const stack = [];
const stackSet = new Set();
let detected = false;
function detect(obj, key) {
if (typeof obj !== 'object') {
return;
}
if (stackSet.has(obj)) { // it's cyclic! Print the object and its locations.
const oldIndex = stack.indexOf(obj);
const l1 = keys.join('.') + '.' + key;
const l2 = keys.slice(0, oldIndex + 1).join('.');
console.log('CIRCULAR: ' + l1 + ' = ' + l2 + ' = ' + obj);
console.log(obj);
detected = true;
return;
}
keys.push(key);
stack.push(obj);
stackSet.add(obj);
for (const k in obj) { // dive on the object's children
if (obj.hasOwnProperty(k)) {
detect(obj[k], k);
}
}
keys.pop();
stack.pop();
stackSet.delete(obj);
return;
}
detect(json, 'obj');
return detected;
}
}
【讨论】：
这里是@Thomas's answer 适用于节点：
const {logger} = require("../logger")
// Or: const logger = {debug: (...args) => console.log.call(console.log, args) }
const joinStrings = (arr, separator) => {
if (arr.length === 0) return "";
return arr.reduce((v1, v2) => `${v1}${separator}${v2}`);
}
exports.CircularReferenceDetector = class CircularReferenceDetector {
detectCircularReferences(toBeStringifiedValue, serializationKeyStack = []) {
Object.keys(toBeStringifiedValue).forEach(key => {
let value = toBeStringifiedValue[key];
let serializationKeyStackWithNewKey = serializationKeyStack.slice();
serializationKeyStackWithNewKey.push(key);
try {
JSON.stringify(value);
logger.debug(`path "${joinStrings(serializationKeyStack)}" is ok`);
} catch (error) {
logger.debug(`path "${joinStrings(serializationKeyStack)}" JSON.stringify results in error: ${error}`);
let isCircularValue;
let circularExcludingStringifyResult = "";
try {
circularExcludingStringifyResult = JSON.stringify(value, this.replaceRootStringifyReplacer(value), 2);
isCircularValue = true;
} catch (error) {
logger.debug(`path "${joinStrings(serializationKeyStack)}" is not the circular source`);
this.detectCircularReferences(value, serializationKeyStackWithNewKey);
isCircularValue = false;
}
if (isCircularValue) {
throw new Error(`Circular reference detected:\nCircularly referenced value is value under path "${joinStrings(serializationKeyStackWithNewKey)}" of the given root object\n`+
`Calling stringify on this value but replacing itself with [Circular object --- fix me] ( <-- search for this string) results in:\n${circularExcludingStringifyResult}\n`);
}
}
});
}
replaceRootStringifyReplacer(toBeStringifiedValue) {
let serializedObjectCounter = 0;
return function (key, value) {
if (serializedObjectCounter !== 0 && typeof(toBeStringifiedValue) === 'object' && toBeStringifiedValue === value) {
logger.error(`object serialization with key ${key} has circular reference to being stringified object`);
return '[Circular object --- fix me]';
}
serializedObjectCounter++;
return value;
}
}
}
【讨论】：
这是对typeof obj != 'object' 条件下@Trey Mack 和@Freddie Nfbnm 答案的修复。相反，它应该测试obj 值是否不是对象的实例，以便在检查对象熟悉的值时也可以工作（例如，函数和符号（符号不是对象的实例，但仍然解决，顺便说一句。））。
由于我还不能在此 StackExchange 帐户中发表评论，因此我将其发布为答案。
PS.：请随时要求我删除此答案。
function isCyclic(obj) {
var keys = [];
var stack = [];
var stackSet = new Set();
var detected = false;
function detect(obj, key) {
if (!(obj instanceof Object)) { return; } // Now works with other
// kinds of object.
if (stackSet.has(obj)) { // it's cyclic! Print the object and its locations.
var oldindex = stack.indexOf(obj);
var l1 = keys.join('.') + '.' + key;
var l2 = keys.slice(0, oldindex + 1).join('.');
console.log('CIRCULAR: ' + l1 + ' = ' + l2 + ' = ' + obj);
console.log(obj);
detected = true;
return;
}
keys.push(key);
stack.push(obj);
stackSet.add(obj);
for (var k in obj) { //dive on the object's children
if (obj.hasOwnProperty(k)) { detect(obj[k], k); }
}
keys.pop();
stack.pop();
stackSet.delete(obj);
return;
}
detect(obj, 'obj');
return detected;
}
【讨论】：
来自http://blog.vjeux.com/2011/javascript/cyclic-object-detection.html。添加了一行来检测循环在哪里。将其粘贴到 Chrome 开发工具中：
function isCyclic (obj) {
var seenObjects = [];
function detect (obj) {
if (obj && typeof obj === 'object') {
if (seenObjects.indexOf(obj) !== -1) {
return true;
}
seenObjects.push(obj);
for (var key in obj) {
if (obj.hasOwnProperty(key) && detect(obj[key])) {
console.log(obj, 'cycle at ' + key);
return true;
}
}
}
return false;
}
return detect(obj);
}
这是测试：
> a = {}
> b = {}
> a.b = b; b.a = a;
> isCyclic(a)
Object {a: Object}
"cycle at a"
Object {b: Object}
"cycle at b"
true
【讨论】：
seenObjects。应该是var seenObjects = [obj];。
detect，这将导致它立即退出，声称从输入对象直接到自身存在一个循环。
var x = {}; JSON.stringify([x,x]) 很好......而var x = {}; x.x = x; JSON.stringify(x); 不是。
obj.hasOwnProperty is not a function。这是在浏览器加载的脚本中运行的。
尝试在 chrome/firefox 浏览器上使用 console.log() 以确定问题所在。
在使用 Firebug 插件的 Firefox 上，您可以逐行调试您的 javascript。
参考下面的循环引用问题示例并已处理：-
// JSON.stringify, avoid TypeError: Converting circular structure to JSON
// Demo: Circular reference
var o = {};
o.o = o;
var cache = [];
JSON.stringify(o, function(key, value) {
if (typeof value === 'object' && value !== null) {
if (cache.indexOf(value) !== -1) {
// Circular reference found, discard key
alert("Circular reference found, discard key");
return;
}
alert("value = '" + value + "'");
// Store value in our collection
cache.push(value);
}
return value;
});
cache = null; // Enable garbage collection
var a = {b:1};
var o = {};
o.one = a;
o.two = a;
// one and two point to the same object, but two is discarded:
JSON.stringify(o);
var obj = {
a: "foo",
b: obj
};
var replacement = {"b":undefined};
alert("Result : " + JSON.stringify(obj,replacement));
参考示例LIVE DEMO
【讨论】：
JSON.stringify() 不是用 JavaScript 实现的，而是用原生代码实现的。你不能用 Firebug 调试它。
var x = {}; JSON.stringify([x,x]) 很好......而var x = {}; x.x = x; JSON.stringify(x); 不是。
我刚做了这个。它可能很脏，但无论如何都可以使用...：P
function dump(orig){
var inspectedObjects = [];
console.log('== DUMP ==');
(function _dump(o,t){
console.log(t+' Type '+(typeof o));
for(var i in o){
if(o[i] === orig){
console.log(t+' '+i+': [recursive]');
continue;
}
var ind = 1+inspectedObjects.indexOf(o[i]);
if(ind>0) console.log(t+' '+i+': [already inspected ('+ind+')]');
else{
console.log(t+' '+i+': ('+inspectedObjects.push(o[i])+')');
_dump(o[i],t+'>>');
}
}
}(orig,'>'));
}
然后
var a = [1,2,3], b = [a,4,5,6], c = {'x':a,'y':b};
a.push(c); dump(c);
说
== DUMP ==
> Type object
> x: (1)
>>> Type object
>>> 0: (2)
>>>>> Type number
>>> 1: (3)
>>>>> Type number
>>> 2: (4)
>>>>> Type number
>>> 3: [recursive]
> y: (5)
>>> Type object
>>> 0: [already inspected (1)]
>>> 1: (6)
>>>>> Type number
>>> 2: (7)
>>>>> Type number
>>> 3: (8)
>>>>> Type number
这说明 c.x[3] 等于 c，并且 c.x = c.y[0]。
或者，稍微修改一下这个函数就可以告诉你你需要什么......
function findRecursive(orig){
var inspectedObjects = [];
(function _find(o,s){
for(var i in o){
if(o[i] === orig){
console.log('Found: obj.'+s.join('.')+'.'+i);
return;
}
if(inspectedObjects.indexOf(o[i])>=0) continue;
else{
inspectedObjects.push(o[i]);
s.push(i); _find(o[i],s); s.pop(i);
}
}
}(orig,[]));
}
【讨论】：
inspectedObjects 数组应该包含原始 JSON 对象本身（即它应该是 var inspectedObjects = [orig];）。
if(o[i] === orig)）和其他对象（inspectedObjects.indexOf(o[i])）。
var x = {}; JSON.stringify([x,x]) 很好......而var x = {}; x.x = x; JSON.stringify(x); 不是。