obj-props: JavaScript Object Property Lists

Common errors

• ERR_REQUIRE_ESM

  cause Attempting to import `obj-props` using `require()` in an ES module context or when the package is primarily designed as an ES module, which prevents synchronous `require` calls.
  fix Use the ES module `import` syntax: `import objProps from 'obj-props';`

• TypeError: objProps is not a function

  cause Mistakenly treating the `objProps` export as a callable function or class constructor instead of a plain JavaScript object that serves as a data map.
  fix Access `objProps` directly as an object, for example, `objProps.Array` or `Object.keys(objProps)`.

• Property 'X' does not exist on type 'Record<string, string[]>' (TypeScript error)

  cause Attempting to access a property (e.g., `objProps.MyCustomObject`) that is not explicitly part of the `objProps` object's inferred type or included in the static JSON data, which primarily covers built-in JavaScript intrinsics.
  fix Access the property with optional chaining (`objProps.MyCustomObject?.propertyName`) or use a type assertion (`(objProps as Record<string, string[]>).MyCustomObject`) if you are confident it exists, or check `Object.keys(objProps)` for available properties. Remember it only contains built-in objects.

Warnings

• breaking The package explicitly requires Node.js version 18.0.0 or higher. Installation or execution in older Node.js environments will fail due to engine restrictions.
  Fix: Upgrade your Node.js environment to version 18.0.0 or later to ensure compatibility.
• breaking This package is a fork of Sindre Sorhus's `proto-props`. While it offers similar functionality, there may be divergences in the data structure, the set of covered properties, or future maintenance. Users migrating from `proto-props` should carefully review the contents and changelog for `obj-props` to understand any behavioral or data differences.
  Fix: Review the `obj-props.json` file and the package's changelog, especially when migrating from `proto-props`, to identify any breaking changes in data or behavior.
• breaking As a major version (`2.0.0`), there may be breaking changes in the structure or content of the `objProps` data object compared to previous major versions. Always consult the release notes when upgrading between major versions.
  Fix: Consult the `obj-props` release notes or directly inspect the `obj-props.json` file when upgrading from a previous major version to understand any data structure changes.
• gotcha The `obj-props` package provides a static snapshot of JavaScript object properties. Its data is generated at build time (via `npm run generate`) and does not dynamically reflect runtime changes to object prototypes or properties in your specific JavaScript environment. New ECMAScript features or host object properties will only be included in new package versions.
  Fix: Understand that the data is fixed for the installed package version. If you require dynamic reflection of an object's current properties at runtime, use `Object.getOwnPropertyNames()`, `Object.keys()`, or `Reflect.ownKeys()`.

Install

• npm install obj-props npm
• yarn add obj-props yarn
• pnpm add obj-props pnpm

Imports

• objProps

  import objProps from 'obj-props';

  This is the primary and recommended way to import the package, utilizing its default ES Module export. It imports the entire properties object.
• objProps
  wrong:

  const objProps = require('obj-props');

  correct:
  Attempting to use CommonJS `require()` will result in an `ERR_REQUIRE_ESM` error if the consuming project is set up as an ES module or if `obj-props` itself declares `"type": "module"` in its `package.json`. Node.js 18+ environments, especially with modern package configurations, heavily favor ES Modules.
• Array, Object (example named exports)
  wrong:

  import { Array, Object } from 'obj-props';

  correct:
  The `obj-props` package provides a single default export which is the entire object containing all properties. It does not export individual intrinsic object property lists as named exports. Trying to destructure named exports from it will fail, as 'Array' or 'Object' are keys within the default-exported object, not top-level exports of the module itself.

Quickstart

Demonstrates importing the obj-props object and accessing properties for various built-in JavaScript constructors, including safe iteration.

import objProps from 'obj-props';

// objProps contains a mapping of JavaScript intrinsic object names to their properties.
// For example, to see properties of the Array constructor:
console.log('Array Constructor Properties:', objProps.Array);

// To access properties of the Object constructor:
console.log('Object Constructor Properties:', objProps.Object);

// The entire data structure can be iterated or accessed directly.
// For instance, to list all known intrinsic objects and their property counts:
console.log('\n--- All Intrinsic Objects and Property Counts ---');
for (const constructorName in objProps) {
  if (Object.prototype.hasOwnProperty.call(objProps, constructorName)) {
    const properties = objProps[constructorName];
    console.log(`${constructorName}: ${properties.length} properties`);
  }
}

// Example: Check if 'Promise' properties are listed and access them safely
const promiseProps = objProps.Promise;
if (promiseProps) {
  console.log('\nPromise Constructor Properties (first 3):', promiseProps.slice(0, 3));
} else {
  console.log('\nPromise properties not explicitly listed or available in this version.');
}