noXorAsExponentiation (JavaScript)

Language JavaScript (and super languages)

Summary

Diagnostic Category: lint/nursery/noXorAsExponentiation
This rule has an unsafe fix.
The default severity of this rule is warning.
Sources:
- Same as unicorn/no-xor-as-exponentiation

How to configure

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{
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  "linter": {
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    "rules": {
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      "nursery": {
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        "noXorAsExponentiation": "error"
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      }
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    }
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  }
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}

Description

Disallow the bitwise XOR operator where exponentiation was likely intended.

In JavaScript, ^ is the bitwise XOR operator, not exponentiation. Developers coming from languages like Lua, Julia, R, or MATLAB, or from math notation, often expect ^ to mean “to the power of”, so 2 ^ 32 silently evaluates to 34 instead of 4294967296. The actual exponentiation operator is **.

This rule flags ^ between two decimal integer literals, which is almost always this mistake. Hexadecimal, octal, and binary literals (such as 0xFF ^ 8) and any non-literal operands (such as flags ^ MASK) are ignored, since those are far more likely to be intentional bitwise XOR.

Examples

Invalid

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const kibibyte = 2 ^ 10; // 8, not 1024

code-block.js:1:20 lint/nursery/noXorAsExponentiation  FIXABLE  ━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━

  ⚠ This bitwise XOR operator ^ is used between two integer literals.
  
  > 1 │ const kibibyte = 2 ^ 10; // 8, not 1024
      │                    ^
    2 │ 
  
  ℹ In JavaScript, ^ is the bitwise XOR operator, not exponentiation. The exponentiation operator is **.
  
  ℹ This rule belongs to the nursery group, which means it is not yet stable and may change in the future. Visit https://biomejs.dev/linter/#nursery for more information.
  
  ℹ Unsafe fix: Replace ^ with **.
  
    1   │ - const·kibibyte·=·2·^·10;·//·8,·not·1024
      1 │ + const·kibibyte·=·2·**·10;·//·8,·not·1024
    2 2 │

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const cube = 3 ^ 3; // 0, not 27

code-block.js:1:16 lint/nursery/noXorAsExponentiation  FIXABLE  ━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━

  ⚠ This bitwise XOR operator ^ is used between two integer literals.
  
  > 1 │ const cube = 3 ^ 3; // 0, not 27
      │                ^
    2 │ 
  
  ℹ In JavaScript, ^ is the bitwise XOR operator, not exponentiation. The exponentiation operator is **.
  
  ℹ This rule belongs to the nursery group, which means it is not yet stable and may change in the future. Visit https://biomejs.dev/linter/#nursery for more information.
  
  ℹ Unsafe fix: Replace ^ with **.
  
    1   │ - const·cube·=·3·^·3;·//·0,·not·27
      1 │ + const·cube·=·3·**·3;·//·0,·not·27
    2 2 │

Valid

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const kibibyte = 2 ** 10;
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const cube = 3 ** 3;
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const masked = flags ^ MASK;
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const bits = 0xFF ^ 8;