no-mixed-enums.md

Pattern: Mixed value types in enum members

Issue: -

Description

Mixing numeric and string values in a single enum creates confusing behavior, especially when iterating over enum values. With mixed enums, iteration methods like Object.values() will include both the numeric keys and values, leading to unexpected results.

Examples

Example of incorrect code:

// Mixed number and string values
enum Status {
  Active = 0,
  Pending = 'PENDING',
  Done = 1
}

// Implicit numbers with string
enum Result {
  Success,
  Error = 'ERROR',
  Unknown
}

// Computed values mixing types
enum Operation {
  Read = 1,
  Write = 1 << 1,
  Execute = 'EXECUTE'
}

// Mixed types with aliases
enum Permission {
  None = 0,
  Basic = None,
  Admin = 'ADMIN'
}

Example of correct code:

// All numeric enum
enum Status {
  Active = 0,
  Pending = 1,
  Done = 2
}

// All string enum
enum Result {
  Success = 'SUCCESS',
  Error = 'ERROR',
  Unknown = 'UNKNOWN'
}

// Numeric enum with computations
enum Permission {
  None = 0,
  Read = 1 << 0,
  Write = 1 << 1,
  Execute = 1 << 2
}

// String enum with consistent values
enum Operation {
  Read = 'READ',
  Write = 'WRITE',
  Execute = 'EXECUTE'
}

// Using separate enums for different types
enum NumericStates {
  Active = 1,
  Inactive = 0
}

enum StringStates {
  Active = 'ACTIVE',
  Inactive = 'INACTIVE'
}