Enum Alternatives: as const Objects Are Safer Than TypeScript Enums

TypeScript numeric enums have surprising behavior: numeric values are assignable to any enum type, reverse mappings pollute the compiled output, and they don't tree-shake well.

Use 'as const' objects instead of enums for safer, tree-shakeable, and more predictable behavior.

// BAD: numeric enum with surprising behavior
enum Direction { Up, Down, Left, Right }
const d: Direction = 999; // TypeScript allows this!

// GOOD: as const object
const Direction = {
  Up: 'UP',
  Down: 'DOWN',
  Left: 'LEFT',
  Right: 'RIGHT',
} as const;

type Direction = typeof Direction[keyof typeof Direction];
// 'UP' | 'DOWN' | 'LEFT' | 'RIGHT'

function move(dir: Direction) { /* ... */ }
move(Direction.Up); // OK
move('INVALID');    // Error
move(999);          // Error — no numeric escape hatch

Numeric enums in TypeScript allow any number to be assigned due to index reverse-mapping. String enums are safer but still generate extra runtime code. 'as const' objects compile to a plain object with zero overhead.