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no-unnecessary-as-const

Disallow unnecessary as const assertions.

Targeted pattern scope​

This rule targets as const assertions inside variable declarators when they are likely redundant:

  • {} as const in variable initializers, and
  • any as const initializer when the variable already has an explicit type annotation.

This is intentionally narrow and does not report every possible redundant as const usage.

What this rule reports​

This rule reports as const assertions that do not provide additional value, such as empty object assertions or assertions on values already constrained by explicit type annotations.

Why this rule exists​

Redundant as const assertions add noise and can imply extra type precision where none is actually gained.

❌ Incorrect​

type I = { value: number };

const x = {} as const;
const y: I = { value: 1 } as const;

✅ Correct​

const z = { value: 1 } as const;

Behavior and migration notes​

This rule reports only and does not provide an autofix.

Remove the assertion when it does not change the effective type contract.

Options​

This rule has no options.

Additional examples​

const options: Readonly<Record<string, string>> = {
 mode: "strict",
} as const;
// ❌ reported because variable already has explicit type annotation

const tuple = ["a", "b"] as const;
// ✅ currently not targeted by this rule

ESLint flat config example​

import etcMisc from "eslint-plugin-etc-misc";

export default [
 {
  plugins: { "etc-misc": etcMisc },
  rules: {
   "etc-misc/no-unnecessary-as-const": "error",
  },
 },
];

When not to use it​

Disable this rule if your team prefers to keep as const for explicitness, even when type annotations already constrain the value.

Package documentation​

Rule catalog ID: R045

Further reading​

Adoption resources​

  • Start at warning level in CI, then move to error after cleanup.
  • Use focused codemods/autofix batches per package or directory.