Nodejs class that is self describing into a file - node.js

Question

Maybe this is basic stuff and things I want to do is really simple, but being a bit junior in Javascript I cannot find any answer to my issue.
What I want to achieve is that from code (in runtime) I want a file to be generated containing all properties and methods (including parameters and if possible return values) described.
Console logging this.__proto__ and Object.keys(this) prints somewhat what I expect.
However, using the Object.keys(this.__proto__) does not return anything useable. I guess this is somehow connected to the fact that the __proto__ contains functions, which are fx. not parsable with JSON.parse().
Any ideas how to approach this?
Test code I used:
const fs = require('fs');
class Exporter {
constructor(name) {
this.filename = `./${name}.export`;
}
export(me) {
let file = '';
let d
d = Object.keys(me);
for (let i = 0; i < d.length; i++) { file += d[i] + '\n'; }
d = Object.keys(me.__proto__);
for (let i = 0; i < d.length; i++) { file += d[i] + '\n'; }
fs.writeFileSync(this.filename, file);
}
}
class Box {
constructor(name, length, width, height) {
this.name = name;
this.length = length;
this.width = width;
this.height = height;
this._export = new Exporter(this.name);
this._export.export(this);
}
volume() {
return this.length * this.height * this.width;
}
}
myBox = new Box('Matts', 2, 3, 4); //creates file Matts.export
console.log(myBox.volume()); //prints '24'
File "Matts.export" written contains:
name
length
width
height
_export
So basically the Objects.keys(me.__proto__) returned a zero length array. I did expect the volume function stated. Preferably with parameters and return value. But I guess the later is hard to achieve in JavaScript.

Answer 1

Because those properties are not enumerable, you can check by using Object.getOwnPropertyDescriptors()
class Box {
constructor(name, length, width, height) {
this.name = name;
this.length = length;
this.width = width;
this.height = height;
}
volume() {
return this.length * this.height * this.width;
}
}
let myBox = new Box("Matts",2,3,4);
console.log(Object.getOwnPropertyDescriptors(myBox.__proto__));
However,Object.getOwnPropertyDescriptors() returns an object which have the same keys as the given object. So you can get the keys from the descriptors:
class Box {
constructor(name, length, width, height) {
this.name = name;
this.length = length;
this.width = width;
this.height = height;
}
volume() {
return this.length * this.height * this.width;
}
}
let myBox = new Box("Matts",2,3,4);
console.log(Object.keys(Object.getOwnPropertyDescriptors(myBox.__proto__)));