object-id

A simple utility function that creates and returns incremental object IDs

Installation

Use npm to install @axaptional/object-id:

$ npm install @axaptional/object-id

Usage

This package is actually just a tiny wrapper around a WeakMap.

Therefore:

• only objects may be mapped to an ID.
• attempting to retrieve the ID of a primitive value will raise a TypeError.
  • (primitives are Boolean, Null, Undefined, Number, String and Symbol)
• IDs are equal when their objects are strictly equal (===).

Import

Import the id object from this package:

// ES2015+ syntax
import { id } from '@axaptional/object-id';
// CommonJS syntax (Node)
const { id } = require('@axaptional/object-id');

id(<object>)

To retrieve an ID for a given object, use id(<object>) or id.id(<object>):

const square = x => x * x;
const idBefore = id(square);
square.squaresNumbers = true;
const idAfter = id(square);
console.log(idBefore === idAfter); // prints "true"

The second variant can come in handy if you already have an "id" module imported and do not want to add a suffix to the alias:

import { id as Axaptional } from '@axaptional/object-id';
Axaptional.id({});

has(<object>, <id>)

To check an object against an ID, use id.has(<object>, <id>):

let square = x => x * x;
const squareId = id(square);
square = x => Math.pow(x, 2);
console.log(id.has(square, squareId)); // prints "false"

clear()

To clear the object ID store, use id.clear():

const square = x => x * x;
const squareId = id(square);
id.clear();
console.log(id.has(square, squareId)); // prints "false"

It is guaranteed that identifying an object both before and after a call to clear() will yield different IDs as long as you do not attempt to identify more objects than Number.MAX_SAFE_INTEGER in total. In other words, calling clear() does not reset the ID counter.

Sidenote

Of course, if you want to check if two objects have the same ID, you do not need to rely on id at all and can instead simply compare the two objects with ===. Strictly unequal objects have different IDs, while strictly equal objects always have the same ID.

License

This package is available under the Unlicense.