noAccidentalBitwiseOperators (JavaScript)

Language JavaScript (and super languages)

Summary

Rule available since: v2.6.0
Diagnostic Category: lint/nursery/noAccidentalBitwiseOperators
This rule has an unsafe fix.
The default severity of this rule is warning.
Sources:
- Same as unicorn/no-accidental-bitwise-operator

How to configure

1
{
2
  "linter": {
3
    "rules": {
4
      "nursery": {
5
        "noAccidentalBitwiseOperators": "error"
6
      }
7
    }
8
  }
9
}

Description

Disallow bitwise operators where a logical operator was likely intended.

The bitwise operators &, |, and |= look a lot like the logical operators &&, ||, and ||=, so it is easy to type one when you meant the other. The two behave very differently:

Bitwise operators always evaluate both sides. In obj & obj.prop, obj.prop is read even when obj is null or undefined, which throws an error.
Bitwise operators turn both sides into whole numbers. In options | {}, the object becomes 0, so the result is a number instead of options or {}.

This rule only reports cases where a logical operator was clearly intended:

& between a variable and a property of that same variable, such as obj & obj.prop.
| or |= with a right side that can never be a useful number: an object, an array, a class, a function, a string, a template string, or true/false.

Bitwise math such as flags & MASK or value | 0 is not reported.

Examples

Invalid

1
if (obj & obj.prop) {}

code-block.js:1:9 lint/nursery/noAccidentalBitwiseOperators  FIXABLE  ━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━

  ⚠ The bitwise operator & is used where the logical operator && was likely intended.
  
  > 1 │ if (obj & obj.prop) {}
      │         ^
    2 │ 
  
  ℹ Bitwise operators always evaluate both sides and turn them into numbers, so the result is not the value of either side.
  
  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 │ if·(obj·&&·obj.prop)·{}
      │          +

1
options = options | {};

code-block.js:1:19 lint/nursery/noAccidentalBitwiseOperators  FIXABLE  ━━━━━━━━━━━━━━━━━━━━━━━━━━━━━

  ⚠ The bitwise operator | is used where the logical operator || was likely intended.
  
  > 1 │ options = options | {};
      │                   ^
    2 │ 
  
  ℹ Bitwise operators always evaluate both sides and turn them into numbers, so the result is not the value of either side.
  
  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 │ options·=·options·||·{};
      │                    +

1
input |= "";

code-block.js:1:7 lint/nursery/noAccidentalBitwiseOperators  FIXABLE  ━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━

  ⚠ The bitwise operator |= is used where the logical operator ||= was likely intended.
  
  > 1 │ input |= "";
      │       ^^
    2 │ 
  
  ℹ Bitwise operators always evaluate both sides and turn them into numbers, so the result is not the value of either side.
  
  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 │ input·||=·"";
      │        +

Valid

1
if (obj && obj.prop) {}
2
options = options || {};
3
input ||= "";
4
const masked = flags & MASK;
5
const truncated = value | 0;