Chrome sendrequest error: TypeError: Converting circular structure to JSON
I've got the following...
chrome.extension.sendRequest({
req: "getDocument",
docu: pagedoc,
name: 'name'
}, function(response){
var efjs = response.reply;
});
which calls the following..
case "getBrowserForDocumentAttribute":
alert("ZOMG HERE");
sendResponse({
reply: getBrowserForDocumentAttribute(request.docu,request.name)
});
break;
However, my code never reaches "ZOMG HERE" but rather throws the following error while running chrome.extension.sendRequest
Uncaught TypeError: Converting circular structure to JSON
chromeHidden.JSON.stringify
chrome.Port.postMessage
chrome.initExtension.chrome.extension.sendRequest
suggestQuery
Does anyone have any idea what is causing this?
It means that the object you pass in the request (I guess it is pagedoc ) has a circular reference, something like:
var a = {};
a.b = a;
JSON.stringify cannot convert structures like this.
NB : This would be the case with DOM nodes, which have circular references, even if they are not attached to the DOM tree. Each node has an ownerDocument which refers to document in most cases. document has a reference to the DOM tree at least through document.body and document.body.ownerDocument refers back to document again, which is only one of multiple circular references in the DOM tree.
As per the JSON docs at Mozilla, JSON.Stringify has a second parameter censor which can be used to filter/ignore children items while parsing the tree. However, perhaps you can avoid the circular references.
In Node.js we cannot. So we can do something like this:
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)));
The result:
Censoring: { foo: { bar: [Circular] } }
Result: {"foo":{"bar":"[Circular]"}}
Unfortunately there seems to be a maximum of 30 iterations before it automatically assumes it's circular. Otherwise, this should work. I even used areEquivalent from here, but JSON.Stringify still throws the exception after 30 iterations. Still, it's good enough to get a decent representation of the object at a top level, if you really need it. Perhaps somebody can improve upon this though? In Node.js for an HTTP request object, I'm getting:
{
"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]"
}
I created a small Node.js module to do this here: https://github.com/ericmuyser/stringy Feel free to improve/contribute!
One approach is to strip object and functions from main object. And stringify the simpler form
function simpleStringify (object){
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
};