noUselessEscapeInString

CSS

Summary

• Rule available since: v2.0.0
• Diagnostic Category: lint/suspicious/noUselessEscapeInString
• This rule is recommended, which means is enabled by default.
• This rule has a safe fix.
• The default severity of this rule is warning.

How to configure

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

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

code-block.css:2:14 lint/suspicious/noUselessEscapeInString  FIXABLE  ━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━

  ⚠ The character doesn’t need to be escaped.
  
    1 │ a::after {
  > 2 │   content: “\a”
      │              ^
    3 │ }
    4 │ 
  
  ℹ Only quotes that enclose the string and special characters need to be escaped.
  
  ℹ Safe fix: Unescape the character.
  
    2 │ ··content:·“\a”
      │             -  

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

code-block.css:2:14 lint/suspicious/noUselessEscapeInString  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:·”\’”
      │             -  

Valid

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

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

Related links

• Disable a rule
• Configure the code fix
• Rule options
• Source Code
• Test Cases

JavaScript (and super languages)

Summary

• Rule available since: v2.0.0
• Diagnostic Category: lint/suspicious/noUselessEscapeInString
• This rule is recommended, which means is enabled by default.
• This rule has a safe fix.
• The default severity of this rule is warning.

How to configure

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

const s = "\a";

code-block.js:1:13 lint/suspicious/noUselessEscapeInString  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”;
      │            -   

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

code-block.js:2:7 lint/suspicious/noUselessEscapeInString  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,
      │      -      

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

code-block.js:1:17 lint/suspicious/noUselessEscapeInString  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·=·$&#123;0&#125;<span style="color: Tomato;">&#92;</span>a;
      │                -   

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:

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

Related links

• Disable a rule
• Configure the code fix
• Rule options
• Source Code
• Test Cases