Prototypes

JavaScript uses a prototypal inheritance model to support OOP. Surprisingly, the set of tools to work with prototypes is relatively small:

• Object.getPrototypeOf()
• Object.setPrototypeOf()

This module contains a set of utilities to work with prototypes.

prototypes.js

The following utilities are available:

Function	Return value	Description
prototypes(object, skipSelf)	generator	Iterate over prototypes.
getPropertyDescriptor(object, name)	descriptor	Get property descriptor from all prototypes.

prototypes() is a generator that yields all prototypes of an object. It starts with the object itself and walks the prototype chain, stopping before Object.prototype — neither it nor null is ever yielded. The object itself is skipped if skipSelf is truthy.

getPropertyDescriptor() is similar to Object.getOwnPropertyDescriptor(), but returns the descriptor of the effective property in all prototypes. Because it is built on prototypes(), properties defined on Object.prototype (toString, hasOwnProperty, …) are not found — the walk is about the object's own inheritance chain, not the language plumbing every object shares.

Examples

import {prototypes, getPropertyDescriptor} from 'meta-toolkit/prototypes.js';

class Foo {
  foo() {
    return 'foo';
  }
}

class Bar extends Foo {
  bar() {
    return 'bar';
  }
}

const x = new Bar();

for (const proto of prototypes(x)) {
  // x
  // Bar
  // Foo
  console.log(proto.constructor?.name); // Bar, Bar, Foo
}

Object.getOwnPropertyDescriptor(x, 'foo'); // undefined
getPropertyDescriptor(x, 'foo'); // real descriptor

Object.getOwnPropertyDescriptor(x, 'bar'); // undefined
getPropertyDescriptor(x, 'bar'); // real descriptor

Exports

All functions are exported by their names. There is no default export.