Exploring the Response Object in Express JS: A Comprehensive Guide

I'm currently using Express version 4.13.4.

My goal is to access and examine the res object. However, when I try to use console.log() on it, the output is too lengthy to display properly in a command window.

I attempted to utilize jsonfile to save it as a .json file. Unfortunately, the object seems to contain self-references, resulting in an error:

TypeError: Converting circular structure to JSON

Is anyone aware of which parts of the res object are causing this circular reference..? One possible solution could involve creating a duplicate of the object and eliminating those sections, allowing the remainder of the object to be viewed.

let resCopy = res;
resCopy.circularProp = null;
// save to a file

I may not have a full grasp of what constitutes a circular structure, so please correct me if needed.

What would be the most effective method to examine the contents of the res object..?

javascriptjsonexpress

Answer №1

One great feature of the util.inspect() function from the node.js built-in library is its ability to handle JavaScript objects with functions or circular structures without encountering errors. Here's how you can use it:

const fs = require("fs");
const util = require("util");
const resAsString = util.inspect(res);
fs.writeFileSync("inspect-res.json", resAsString, "utf8");

With this code snippet, the res object will be converted into a string that resembles JSON format and saved in the inspect-res.json file with proper formatting.

In case you're wondering, circular structure refers to objects that have references pointing back to themselves, creating an infinite depth loop like res.obj1.obj2.obj1.obj2.obj1.obj2...

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