Enable constants as computed values for string enums · Issue #40793 · microsoft/TypeScript (original) (raw)

Search Terms

'TS18033', 'typescript define enum with constant string value', 'string enum computed constant'

Suggestion

Please consider enabling to use constant variables as values for string enums. The following code snippet fails compilation with TS18033 ('Only numeric enums can have computed members, but this expression has type 'string'. If you do not need exhaustiveness checks, consider using an object literal instead.')

const VALUE: string = 'ENUM_VALUE';

enum MyEnum { KEY = VALUE, // <-- Fails with TS18033 }

console.log(MyEnum.KEY);

, whereas the following passes:

enum Values { VALUE = 'ENUM_VALUE', }

enum MyEnum { KEY = Values.VALUE, }

console.info(MyEnum.KEY);

Use Cases

Use string interpolation (templated strings) when defining the value of a string enum to be able to reuse pre-defined constants as part of the value. (E.g. namespace prefixes, extension postfixes)

Examples

const NAMESPACE: string = 'com.mycompany.myservice';

enum Errors { INVALID_INPUT_ERROR = ${NAMESPACE}.errors#InvalidInput, }

Checklist

My suggestion meets these guidelines: