Enum vs union literal type trade-offs in Typescript - Quick Revision & Key Differences

Recall & Review

beginner

What is a TypeScript enum?

An enum is a special TypeScript type that allows you to define a set of named constants, which can be either numeric or string values.

beginner

What is a union literal type in TypeScript?

A union literal type is a type that can be one of several specific string or numeric literal values, written as a union of those literals.

intermediate

Name one advantage of using enums over union literal types.

Enums provide a clear grouping of related constants and can be used both as types and values, which helps with code organization and readability.

intermediate

What is a key trade-off when choosing union literal types instead of enums?

Union literal types are simpler and generate less JavaScript code, but they lack runtime representation and cannot be iterated over like enums.

beginner

Why might you prefer union literal types for small sets of values?

Because union literal types are lightweight, have no runtime overhead, and provide better type safety with string literal types, making them ideal for small, fixed sets.

Which of the following is true about TypeScript enums?

A They only exist at compile time and generate no code.

B They cannot have string values.

C They generate JavaScript code and have runtime representation.

D They are the same as union literal types.

Enums generate JavaScript code and exist at runtime, unlike union literal types which are erased after compilation.

What is a benefit of union literal types compared to enums?

A They group constants under one object.

B They can be iterated at runtime.

C They allow dynamic value assignment.

D They generate less JavaScript code.

Union literal types are erased during compilation, so they generate no extra JavaScript code.

Which is a limitation of union literal types?

A They cannot be used as types.

B They lack runtime representation for iteration.

C They require explicit numeric values.

D They have runtime overhead.

Union literal types do not exist at runtime, so you cannot iterate over their values.

When might enums be preferred over union literal types?

A When you need to iterate over values at runtime.

B When you want zero runtime code.

C When you want simpler type definitions.

D When you want to avoid grouping constants.

Enums provide runtime objects that can be iterated, unlike union literal types.

Which statement about union literal types is false?

A They generate runtime JavaScript objects.

B They are ideal for small fixed sets of values.

C They provide better type safety with string literals.

D They do not support iteration at runtime.

Union literal types do not generate runtime JavaScript objects; they exist only at compile time.

Explain the main differences between enums and union literal types in TypeScript.

Think about runtime presence and code generation.

Describe scenarios where you would choose union literal types over enums and vice versa.

Consider runtime needs and code simplicity.