Can a JavaScript Object Know The Identifier Name of its Instance?

To begin with, let me assure you that this is one classic case of “I was too busy thinking whether I could, that I forgot whether I should.”

Of course, I can do this !!!

This started when I stumbled upon this question on SO: How to include or detect the name of a new Object when it’s created from a Constructor

I understand that in most cases your code shouldn’t need to know the identifier name. However, this might have some application in debugging (maybe?) Nevertheless, given the flexibility of JavaScript I was almost certain that this is possible.

So here is my solution for the same. Here I am using anError object to get the current line number and then reading the source file to find the identifier name.

let fs = require('fs');
class Foo {
 constructor(bar) {
  this.bar = bar;
  readIdentifierFromFile(getLineAndFile()).then(identifier => {
   this.identifier = identifier;
  })
 }
 toString() {
  return `bar: ${this.bar}, identifier:${this.identifier}`;
 }
}
let foo = new Foo(5);
setTimeout(() => {
 console.log(foo.toString()); // bar: 5 identifier:foo
}, 2000); // Some delay to allow the source code to be read #bad_code
function getErrorObject(){
    try { throw Error('') } catch(err) { return err; }
}
function getLineAndFile() {
 let err = getErrorObject();
 let callerLine = err.stack.split("\n")[5];
 let index = callerLine.indexOf("(");
 return callerLine.slice(index+1, callerLine.length-1);
}
function readIdentifierFromFile(lineAndFile) {
 let file = lineAndFile.split(':')[0];
 let line = lineAndFile.split(':')[1];
 return new Promise((resolve, reject) => {
  fs.readFile(file, 'utf-8', (err, data) => { 
      if (err) {
       reject(err);
      }
      resolve(data.split('\n')[parseInt(line)-1].split('=')[0].trim().split(' ')[1]);
  });
 })
}

PS: The code breaks if you assign a new identifier to a reference: let foo2 = foo

Can you think of a valid use-case for such code? Is there any other approach you can think of?