What is the problem with using enum in TypeScript when compiling to JavaScript? What can replace enum?

The problem with using enums in TypeScript when compiling to JavaScript is that TypeScript enums compile into quite verbose code that creates an object with bidirectional mapping (number ↔ string). This increases the size of the final bundle and can lead to unwanted side effects during tree-shaking.

Additionally, enums in TypeScript are a special construct that does not exist in plain JavaScript, which complicates integration with other tools and libraries.

Instead of enums, it is often recommended to use:

• Objects with constants (const objects) with the as const type, which allows for literal types and more lightweight code:

const Colors = {
  Red: "RED",
  Green: "GREEN",
  Blue: "BLUE"
} as const;

type Colors = typeof Colors[keyof typeof Colors];

• Union of string literal types, which provides strict typing without extra code:

type Colors = "RED" | "GREEN" | "BLUE";

This approach reduces the size of the compiled code and improves readability.