Rule proposal: prefer Symbol.for() over Symbol()

[Xunnamius]

Description

From time to time I find myself passing things between realms, usually in Node/Jest but also between workers or frames on the frontend, and I've been bitten by faulty instanceof checks (identity discontinuity) more than once. My solution has been to use Symbols to track an object's type/provenance.

For instance, for a piece of code meant to handle a subset of custom app errors, instead of catch(e) { if(e instanceof AppError) ... } I'll do catch(e) { if(e?.[$type] === 'AppError') ... } where const $type = Symbol('type') and class AppError extends Error { [$type] = 'AppError'; ... }.

However, unlike the well-known Symbols, custom Symbols are only unique at the realm level and so suffer the same identity discontinuity issue as instanceof. But we can create cross-realm Symbols with Symbol.for. Perhaps Symbol.for() should be preferred over Symbol() in all cases?

Fail

const foo = Symbol('foo');

Pass

const foo = Symbol.for('foo');

const foo = Symbol.for('@Xunnamius/foo');

Additional Info

N/A

[fisker]

They are for different purposes.

As for the instanceof problem, you may want try Ergonomic brand checks for Private Fields

[Xunnamius]

I see. Thanks for the link

[sindresorhus]

Passing on this as it's not the correct use of Symbol.for.