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noConstEnum

src/content/docs/linter/rules/no-const-enum.mdx

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<Tabs> <TabItem label="TypeScript and TSX" icon="seti:typescript"> ## Summary - Rule available since: `v1.0.0` - Diagnostic Category: [`lint/suspicious/noConstEnum`](/reference/diagnostics#diagnostic-category) - This rule is **recommended**, meaning it is enabled by default. - This rule has a [**safe**](/linter/#safe-fixes) fix. - The default severity of this rule is [**warning**](/reference/diagnostics#warning). ## How to configure ```json title="biome.json" { "linter": { "rules": { "suspicious": { "noConstEnum": "error" } } } }

## Description
Disallow TypeScript `const enum`

Const enums are enums that should be inlined at use sites.
Const enums are not supported by bundlers and are incompatible with the `isolatedModules` mode.
Their use can lead to import nonexistent values (because const enums are erased).

Thus, library authors and bundler users should not use const enums.

## Examples

### Invalid

```ts
const enum Status {
  Open,
  Close,
}

<pre class="language-text"><code class="language-text">code-block.ts:1:1 <a href="https://biomejs.dev/linter/rules/no-const-enum">lint/suspicious/noConstEnum</a> <span style="color: #000; background-color: #ddd;"> FIXABLE </span> ━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━ <strong><span style="color: Orange;">⚠</span></strong> <span style="color: Orange;">The </span><span style="color: Orange;"><strong>enum declaration</strong></span><span style="color: Orange;"> should not be </span><span style="color: Orange;"><strong>const</strong></span> <strong><span style="color: Tomato;">></span></strong> <strong>1 │ </strong>const enum Status { <strong> │ </strong><strong><span style="color: Tomato;">^</span></strong><strong><span style="color: Tomato;">^</span></strong><strong><span style="color: Tomato;">^</span></strong><strong><span style="color: Tomato;">^</span></strong><strong><span style="color: Tomato;">^</span></strong><strong><span style="color: Tomato;">^</span></strong><strong><span style="color: Tomato;">^</span></strong><strong><span style="color: Tomato;">^</span></strong><strong><span style="color: Tomato;">^</span></strong><strong><span style="color: Tomato;">^</span></strong><strong><span style="color: Tomato;">^</span></strong><strong><span style="color: Tomato;">^</span></strong><strong><span style="color: Tomato;">^</span></strong><strong><span style="color: Tomato;">^</span></strong><strong><span style="color: Tomato;">^</span></strong><strong><span style="color: Tomato;">^</span></strong><strong><span style="color: Tomato;">^</span></strong><strong><span style="color: Tomato;">^</span></strong><strong><span style="color: Tomato;">^</span></strong> <strong><span style="color: Tomato;">></span></strong> <strong>2 │ </strong> Open, <strong><span style="color: Tomato;">></span></strong> <strong>3 │ </strong> Close, <strong><span style="color: Tomato;">></span></strong> <strong>4 │ </strong>} <strong> │ </strong><strong><span style="color: Tomato;">^</span></strong> <strong>5 │ </strong> <strong><span style="color: lightgreen;">ℹ</span></strong> <span style="color: lightgreen;">Const enums are not supported by bundlers and are incompatible with the 'isolatedModules' mode. Their use can lead to import inexistent values.</span> <strong><span style="color: lightgreen;">ℹ</span></strong> <span style="color: lightgreen;">See </span><span style="color: lightgreen;"><a href="https://www.typescriptlang.org/docs/handbook/enums.html#const-enum-pitfalls">TypeScript Docs</a></span><span style="color: lightgreen;"> for more details.</span> <strong><span style="color: lightgreen;">ℹ</span></strong> <span style="color: lightgreen;">Safe fix</span><span style="color: lightgreen;">: </span><span style="color: lightgreen;">Turn the </span><span style="color: lightgreen;"><strong>const enum</strong></span><span style="color: lightgreen;"> into a regular </span><span style="color: lightgreen;"><strong>enum</strong></span><span style="color: lightgreen;">.</span> <strong> 1 │ </strong><span style="color: Tomato;">c</span><span style="color: Tomato;">o</span><span style="color: Tomato;">n</span><span style="color: Tomato;">s</span><span style="color: Tomato;">t</span><span style="opacity: 0.8;"><span style="color: Tomato;">·</span></span>enum<span style="opacity: 0.8;">·</span>Status<span style="opacity: 0.8;">·</span>{ <strong> │ </strong><span style="color: Tomato;">-</span><span style="color: Tomato;">-</span><span style="color: Tomato;">-</span><span style="color: Tomato;">-</span><span style="color: Tomato;">-</span><span style="color: Tomato;">-</span> </code></pre>

Valid

ts

enum Status {
  Open,
  Close,
}

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