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noUselessCatchBinding

src/content/docs/linter/rules/no-useless-catch-binding.mdx

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import { Tabs, TabItem } from '@astrojs/starlight/components';

<Tabs> <TabItem label="JavaScript (and super languages)" icon="seti:javascript"> ## Summary - Rule available since: `v2.2.3` - Diagnostic Category: [`lint/complexity/noUselessCatchBinding`](/reference/diagnostics#diagnostic-category) - This rule isn't recommended, so you need to enable it. - This rule has an [**unsafe**](/linter/#unsafe-fixes) fix. - The default severity of this rule is [**information**](/reference/diagnostics#information). ## How to configure ```json title="biome.json" { "linter": { "rules": { "complexity": { "noUselessCatchBinding": "error" } } } }

## Description
Disallow unused catch bindings.

This rule disallows unnecessary catch bindings in accordance with ECMAScript 2019.
See also: the ECMAScript 2019 “optional catch binding” feature in the language specification.

## Examples

### Invalid

```js
try {
    // Do something
} catch (unused) {}

<pre class="language-text"><code class="language-text">code-block.js:3:9 <a href="https://biomejs.dev/linter/rules/no-useless-catch-binding">lint/complexity/noUselessCatchBinding</a> <span style="color: #000; background-color: #ddd;"> FIXABLE </span> ━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━ <strong><span style="color: lightgreen;">ℹ</span></strong> <span style="color: lightgreen;">This </span><span style="color: lightgreen;"><strong>catch binding</strong></span><span style="color: lightgreen;"> is unused.</span> <strong>1 │ </strong>try { <strong>2 │ </strong> // Do something <strong><span style="color: Tomato;">></span></strong> <strong>3 │ </strong>} catch (unused) {} <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>4 │ </strong> <strong><span style="color: lightgreen;">ℹ</span></strong> <span style="color: lightgreen;">Since ECMAScript 2019, catch bindings are optional; you can omit the catch binding if you don't need it.</span> <strong><span style="color: lightgreen;">ℹ</span></strong> <span style="color: lightgreen;">Unsafe fix</span><span style="color: lightgreen;">: </span><span style="color: lightgreen;">Remove the catch binding.</span> <strong> 3 │ </strong>}<span style="opacity: 0.8;">·</span>catch<span style="opacity: 0.8;">·</span><span style="color: Tomato;">(</span><span style="color: Tomato;">u</span><span style="color: Tomato;">n</span><span style="color: Tomato;">u</span><span style="color: Tomato;">s</span><span style="color: Tomato;">e</span><span style="color: Tomato;">d</span><span style="color: Tomato;">)</span><span style="opacity: 0.8;"><span style="color: Tomato;">·</span></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><span style="color: Tomato;">-</span><span style="color: Tomato;">-</span><span style="color: Tomato;">-</span> </code></pre>

js

try {
    // Do something
} catch ({ unused }) {}

<pre class="language-text"><code class="language-text">code-block.js:3:9 <a href="https://biomejs.dev/linter/rules/no-useless-catch-binding">lint/complexity/noUselessCatchBinding</a> <span style="color: #000; background-color: #ddd;"> FIXABLE </span> ━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━ <strong><span style="color: lightgreen;">ℹ</span></strong> <span style="color: lightgreen;">This </span><span style="color: lightgreen;"><strong>catch binding</strong></span><span style="color: lightgreen;"> is unused.</span> <strong>1 │ </strong>try { <strong>2 │ </strong> // Do something <strong><span style="color: Tomato;">></span></strong> <strong>3 │ </strong>} catch ({ unused }) {} <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>4 │ </strong> <strong><span style="color: lightgreen;">ℹ</span></strong> <span style="color: lightgreen;">Since ECMAScript 2019, catch bindings are optional; you can omit the catch binding if you don't need it.</span> <strong><span style="color: lightgreen;">ℹ</span></strong> <span style="color: lightgreen;">Unsafe fix</span><span style="color: lightgreen;">: </span><span style="color: lightgreen;">Remove the catch binding.</span> <strong> 3 │ </strong>}<span style="opacity: 0.8;">·</span>catch<span style="opacity: 0.8;">·</span><span style="color: Tomato;">(</span><span style="color: Tomato;">{</span><span style="opacity: 0.8;"><span style="color: Tomato;">·</span></span><span style="color: Tomato;">u</span><span style="color: Tomato;">n</span><span style="color: Tomato;">u</span><span style="color: Tomato;">s</span><span style="color: Tomato;">e</span><span style="color: Tomato;">d</span><span style="opacity: 0.8;"><span style="color: Tomato;">·</span></span><span style="color: Tomato;">}</span><span style="color: Tomato;">)</span><span style="opacity: 0.8;"><span style="color: Tomato;">·</span></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><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><span style="color: Tomato;">-</span> </code></pre>

js

try {
    // Do something
} catch ({ unused1, unused2 }) {}

<pre class="language-text"><code class="language-text">code-block.js:3:9 <a href="https://biomejs.dev/linter/rules/no-useless-catch-binding">lint/complexity/noUselessCatchBinding</a> <span style="color: #000; background-color: #ddd;"> FIXABLE </span> ━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━ <strong><span style="color: lightgreen;">ℹ</span></strong> <span style="color: lightgreen;">This </span><span style="color: lightgreen;"><strong>catch binding</strong></span><span style="color: lightgreen;"> is unused.</span> <strong>1 │ </strong>try { <strong>2 │ </strong> // Do something <strong><span style="color: Tomato;">></span></strong> <strong>3 │ </strong>} catch ({ unused1, unused2 }) {} <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><span style="color: Tomato;">^</span></strong><strong><span style="color: Tomato;">^</span></strong> <strong>4 │ </strong> <strong><span style="color: lightgreen;">ℹ</span></strong> <span style="color: lightgreen;">Since ECMAScript 2019, catch bindings are optional; you can omit the catch binding if you don't need it.</span> <strong><span style="color: lightgreen;">ℹ</span></strong> <span style="color: lightgreen;">Unsafe fix</span><span style="color: lightgreen;">: </span><span style="color: lightgreen;">Remove the catch binding.</span> <strong> 3 │ </strong>}<span style="opacity: 0.8;">·</span>catch<span style="opacity: 0.8;">·</span><span style="color: Tomato;">(</span><span style="color: Tomato;">{</span><span style="opacity: 0.8;"><span style="color: Tomato;">·</span></span><span style="color: Tomato;">u</span><span style="color: Tomato;">n</span><span style="color: Tomato;">u</span><span style="color: Tomato;">s</span><span style="color: Tomato;">e</span><span style="color: Tomato;">d</span><span style="color: Tomato;">1</span><span style="color: Tomato;">,</span><span style="opacity: 0.8;"><span style="color: Tomato;">·</span></span><span style="color: Tomato;">u</span><span style="color: Tomato;">n</span><span style="color: Tomato;">u</span><span style="color: Tomato;">s</span><span style="color: Tomato;">e</span><span style="color: Tomato;">d</span><span style="color: Tomato;">2</span><span style="opacity: 0.8;"><span style="color: Tomato;">·</span></span><span style="color: Tomato;">}</span><span style="color: Tomato;">)</span><span style="opacity: 0.8;"><span style="color: Tomato;">·</span></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><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><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><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

js

try {
    // Do something
} catch (used) {
    console.error(used);
}

js

try {
    // Do something
} catch ({ used }) {
    console.error(used);
}

js

try {
    // Do something
} catch ({ used, unused }) {
    console.error(used);
}

js

try {
    // Do something
} catch {}

</TabItem> </Tabs>