noUselessEscapeInString

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

<Tabs> <TabItem label="CSS" icon="seti:css"> ## Summary - Rule available since: `v2.0.0` - Diagnostic Category: [`lint/suspicious/noUselessEscapeInString`](/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": { "noUselessEscapeInString": "error" } } } }

## Description
Disallow unnecessary escapes in string literals.

Escaping non-special characters in string literals doesn't have any effect.
Hence, they may confuse a reader.

## Examples

### Invalid

```css
a::after {
  content: "\z"
}

<pre class="language-text"><code class="language-text">code-block.css:2:14 <a href="https://biomejs.dev/linter/rules/no-useless-escape-in-string">lint/suspicious/noUselessEscapeInString</a> FIXABLE ━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━ ⚠ The character doesn't need to be escaped. 1 │ a::after { > 2 │ content: "\z" │ ^ 3 │ } 4 │ ℹ Only quotes that enclose the string and special characters need to be escaped. ℹ Safe fix: Unescape the character. 2 │ ··content:·"\z" │ - </code></pre>

css

a::after {
  content: "\'"
}

<pre class="language-text"><code class="language-text">code-block.css:2:14 <a href="https://biomejs.dev/linter/rules/no-useless-escape-in-string">lint/suspicious/noUselessEscapeInString</a> FIXABLE ━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━ ⚠ The character doesn't need to be escaped. 1 │ a::after { > 2 │ content: "\'" │ ^ 3 │ } 4 │ ℹ Only quotes that enclose the string and special characters need to be escaped. ℹ Safe fix: Unescape the character. 2 │ ··content:·"\'" │ - </code></pre>

Valid

css

a::after {
  content: "\""
}

css

a::after {
  content: "\n"
}

css

a::after {
  content: "\e7bb"
}

</TabItem> <TabItem label="JavaScript (and super languages)" icon="seti:javascript"> ## Summary - Rule available since: `v2.0.0` - Diagnostic Category: [`lint/suspicious/noUselessEscapeInString`](/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": { "noUselessEscapeInString": "error" } } } }

## Description
Disallow unnecessary escapes in string literals.

Escaping non-special characters in string literals doesn't have any effect.
Hence, they may confuse a reader.

## Examples

### Invalid

```js
const s = "\a";

<pre class="language-text"><code class="language-text">code-block.js:1:13 <a href="https://biomejs.dev/linter/rules/no-useless-escape-in-string">lint/suspicious/noUselessEscapeInString</a> FIXABLE ━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━ ⚠ The character doesn't need to be escaped. > 1 │ const s = "\a"; │ ^ 2 │ ℹ Only quotes that enclose the string and special characters need to be escaped. ℹ Safe fix: Unescape the character. 1 │ const·s·=·"\a"; │ - </code></pre>

const o = {
    "\a": 0,
};

<pre class="language-text"><code class="language-text">code-block.js:2:7 <a href="https://biomejs.dev/linter/rules/no-useless-escape-in-string">lint/suspicious/noUselessEscapeInString</a> FIXABLE ━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━ ⚠ The character doesn't need to be escaped. 1 │ const o = { > 2 │ "\a": 0, │ ^ 3 │ }; 4 │ ℹ Only quotes that enclose the string and special characters need to be escaped. ℹ Safe fix: Unescape the character. 2 │ ····"\a":·0, │ - </code></pre>

const s = `${0}\a`;

<pre class="language-text"><code class="language-text">code-block.js:1:17 <a href="https://biomejs.dev/linter/rules/no-useless-escape-in-string">lint/suspicious/noUselessEscapeInString</a> FIXABLE ━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━ ⚠ The character doesn't need to be escaped. > 1 │ const s = `${0}\a`; │ ^ 2 │ ℹ Only quotes that enclose the string and special characters need to be escaped. ℹ Safe fix: Unescape the character. 1 │ const·s·=·`${0}\a`; │ - </code></pre>

Valid

const s = "\n";

In template literals, \${ and $\{ are valid escapes:

const s = `\${0}`;

Tagged string templates are ignored:

const s = tagged`\a`;

JSX strings are ignored:

jsx

<div attr="str\a"/>;

</TabItem> </Tabs>

Valid

Related links

Valid

Related links