How to print object in Node JS

Question

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('http://ip-api.com/json', (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}`);
  });

Answer 1

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.

Answer 2

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.

Answer 3

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('http://ip-api.com/json', 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
  }
});

Answer 4

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]);
});

Answer 5

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.

Answer 6

Use console.dir and set the depth.

console.dir(obj, { depth:10 })

Alternatively you can set the default depth to change the console.log depth.

require('util').inspect.defaultOptions.depth = 10

All of this and details about this can be found in nodejs training.

https://nodejs.dev/learn/how-to-log-an-object-in-nodejs

Answer 7

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("http://ip-api.com/json", 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

Answer 8

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 :)