In the below code (running on Node JS) I am trying to print an object obtained from an external API using JSON.stringify which results in an error:
TypeError: Converting circular structure to JSON
I have looked at the questions on this topic, but none could help. Could some one please suggest:
a) How I could obtain country value from the res object ?
b) How I could print the entire object itself ?
http.get(' (res) => {
console.log(`Got response: ${res.statusCode}`);
console.log(res.country) // *** Results in Undefined
console.log(JSON.stringify(res)); // *** Resulting in a TypeError: Converting circular structure to JSON
res.resume();
}).on('error', (e) => {
console.log(`Got error: ${e.message}`);
});
7 Answers
Basic console.log will not go through long and complex object, and may decide to just print [Object] instead.
A good way to prevent that in node.js is to use util.inspect:
'use strict';
const util = require('util'),
obj = /*Long and complex object*/;
console.log(util.inspect(obj, {depth: null}));
//depth: null tell util.inspect to open everything until it get to a circular reference, the result can be quite long however.
EDIT: In a pinch (in the REPL for example), a second option is JSON.stringify. No need to require it, but it will break on circular reference instead of printing the fact there is a reference.
Print the whole object, it will not have problems with recursive refferences:
console.log(res);
Here's an example for you to see how console.log handles circular refferences:
> var q = {a:0, b:0}
> q.b = q
> console.log(q)
{ a: 0, b: [Circular] }
Also, I would advise to check what data are you actually receiving.
By using the http request client, I am able to print the JSON object as well as print the country value. Below is my updated code.
var request = require('request');
request(' function (error, response, body) {
if (!error && response.statusCode == 200) {
console.log(response.body); // Prints the JSON object
var object = JSON.parse(body);
console.log(object['country']) // Prints the country value from the JSON object
}
});
This can print the key of the object and the value of the object in the simplest way. Just try it.
const jsonObj = {
a: 'somestring',
b: 42,
c: false
};
Array.from(Object.keys(jsonObj)).forEach(function(key){
console.log(key + ":" + jsonObj[key]);
});
In 2021, I just printed using
app.post("/",(req,res) => {
console.log("HI "+JSON.stringify(req.body));
res.send("Hi")
});
and got my output as HI {"Hi":"Hi"}.
I sent
{
"Hi": "Hi"
}
as my post request body.
Only doing console.log(req.body) printed [object Object] on console but now this works.
You do not actually get data in res. You need on('data') and on.('end')
body is a string. It gets append on data received, so on complete you will need to parse data into json
http.get("", function(res) {
var body = '';
res.on('data', function(data){
body = body + data;
});
res.on('end', function() {
var parsed = {};
try{
parsed = JSON.parse(body); // i have checked its working correctly
}
catch(er){
//do nothing it is already json
}
console.log(parsed.country);
});
});
Noe from parsed which is a json object, you can get any property
You can pass two arguments to console.log()
Try this code after installing "yargs" And it will print whole object
console.log('object is' , yargs.argv);
I think may be it will help you to print whole object :)
