typescript/prefer-as-const Correctness

What it does

Enforce the use of as const over literal type.

Why is this bad?

There are two common ways to tell TypeScript that a literal value should be interpreted as its literal type (e.g. 2) rather than general primitive type (e.g. number);

as const: telling TypeScript to infer the literal type automatically as with the literal type: explicitly telling the literal type to TypeScript

as const is generally preferred, as it doesn't require re-typing the literal value. This rule reports when an as with an explicit literal type can be replaced with an as const.

Examples

Examples of incorrect code for this rule:

let bar: 2 = 2;
let foo = { bar: "baz" as "baz" };

Examples of correct code for this rule:

let foo = "bar";
let foo = "bar" as const;
let foo: "bar" = "bar" as const;
let bar = "bar" as string;
let foo = { bar: "baz" };

How to use

To enable this rule using the config file or in the CLI, you can use:

Config (.oxlintrc.json)

{
  "rules": {
    "typescript/prefer-as-const": "error"
  }
}

CLI

oxlint --deny typescript/prefer-as-const

References

• Rule Source