A More Idiomatic Enum for JavaScript

💡 Ideas
1

A More Idiomatic Enum for JavaScript

  • Idiomatic to JavaScript
  • Semantic
  • Progressive
  • Arbitrary value types
  • Mergeable
  • Straightforward desugaring
  • Straightforward TypeScript typing

Basic Syntax

enum STATUS {
    Ready: 0,
    Pending: 1,
    Done: 2
};

Desugaring: Object + (1. Pure syntactic sugar OR 2. Frozen object)

// Option 1: Pure syntactic sugar (for readability)
const STATUS = {
    Ready: 0,
    Pending: 1,
    Done: 2,
};
// Option 2: Frozen object (with runtime immutability)
const STATUS = Object.freeze({
    Ready: 0,
    Pending: 1,
    Done: 2,
});

Arbitrary Value Types

enum STATUS {
    Ready: 0,
    Pending: "pending",
    Done: true,
    Error: null,
    Warn: {}
}

Merging: {...enum, ...object}

enum APP_STATUS {
    Ready: "ready",
    Pending: "pending",
    Done: "done"
}

enum USER_STATUS {
    LoggedIn: "logged-in",
    LoggedOut: "logged-out"
}

const TEST_STATUS = {
    Success: "success",
    Error: "error"
};

enum STATUS {
    ...APP_STATUS,
    ...USER_STATUS,
    ...TEST_STATUS
}

Design Rationale: No Reverse Mapping

The decision to omit reverse mapping is a deliberate choice to keep the feature idiomatic to JavaScript.

  • Idiomatic & Predictable: JS developers are accustomed to standard object semantics. Adding reverse mapping introduces hidden complexity that breaks the “what you see is what you get” intuition.
  • Rarely Used: In practice, the need for STATUS[1] is extremely rare compared to STATUS.Ready.
  • Ambiguity with Shared Values: Reverse mapping is fundamentally broken when different keys map to the same value. For example, if Ready: 1 and Success: 1 both exist, a reverse mapping like STATUS[1] is ambiguous. Plain objects naturally handle this by just retaining the key-value structure.

For cases where reverse lookup is strictly necessary, developers can easily and explicitly use Object.entries() or Object.keys() to build a reverse map, paying only for what they actually use.

2

Hi @yxdtg

There is an existing proposal for enums. If this is an idea on how that proposal could change it would be best to discuss there.

2 Likes
3

Sure, thanks for the reminder

4

https://www.npmjs.com/package/@jiaozi-dev/kit