enumValueConsistency

Reports enums that contain both string and number members.

✅ This rule is included in the ts logical presets.

TypeScript enums can have members with numeric or string values. While it’s technically possible to mix both types in the same enum, doing so creates confusing iteration behavior.

When you iterate over an enum using Object.keys(), Object.values(), or Object.entries():

• String enums produce exactly the number of items matching enum members
• Numeric enums produce double the items due to reverse mappings (value-to-name mappings)
• Mixed enums produce both numbers and strings

This rule requires all enum members to consistently use either all numbers or all strings.

Examples

❌ Incorrect

enum Status {
  Active = 0,
  Inactive = "inactive",
}

enum Mixed {
  First,
  Second = "second",
}

✅ Correct

enum Status {
  Active = 0,
  Inactive = 1,
}

enum Status {
  Active = "active",
  Inactive = "inactive",
}

enum Direction {
  Up,
  Down,
  Left,
  Right,
}

Options

This rule is not configurable.

When Not To Use It

If you don’t iterate over enums and don’t mind the confusion of mixed enum member values, you may disable this rule. Some codebases intentionally use mixed enums for specific use cases where the iteration behavior is well understood.

Further Reading

• MDN: Object.keys()
• TypeScript Handbook: Enums

Equivalents in Other Linters

• ESLint: @typescript-eslint/no-mixed-enums
• Oxlint: typescript/no-mixed-enums