useMathAbs (JavaScript)

Language JavaScript (and super languages)

Summary

Rule available since: v2.6.3
Diagnostic Category: lint/nursery/useMathAbs
This rule has an unsafe fix.
The default severity of this rule is warning.
Sources:
- Same as unicorn/prefer-math-abs

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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        "useMathAbs": "error"
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      }
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    }
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  }
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}

Description

Prefer Math.abs() over manual absolute value calculations and range checks.

The absolute value of a number is its distance from zero, so it is never negative. Math.abs() states that intent directly. Writing the calculation manually repeats the value for the positive case and for the negative case, which is longer and easier to get wrong.

This rule reports two patterns:

A conditional expression that flips the sign of a value when the value is below zero, such as value < 0 ? -value : value.
A condition that compares the same value with a limit and with the negative of that limit, such as value > limit || value < -limit.

Math.abs() throws an error when its argument is a bigint. The rule ignores a value when its literal, its type annotation, or a BigInt() call shows that it is a bigint.

Examples

Invalid

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const distance = value < 0 ? -value : value;

code-block.js:1:18 lint/nursery/useMathAbs  FIXABLE  ━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━

  ⚠ This conditional expression manually computes an absolute value.
  
  > 1 │ const distance = value < 0 ? -value : value;
      │                  ^^^^^^^^^^^^^^^^^^^^^^^^^^
    2 │ 
  
  ℹ Math.abs() expresses this directly and avoids repeating the value for the positive and negative cases.
  
  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: Use Math.abs() instead.
  
    1   │ - const·distance·=·value·<·0·?·-value·:·value;
      1 │ + const·distance·=·Math.abs(value);
    2 2 │

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const distance = value >= 0 ? value : 0 - value;

code-block.js:1:18 lint/nursery/useMathAbs  FIXABLE  ━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━

  ⚠ This conditional expression manually computes an absolute value.
  
  > 1 │ const distance = value >= 0 ? value : 0 - value;
      │                  ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
    2 │ 
  
  ℹ Math.abs() expresses this directly and avoids repeating the value for the positive and negative cases.
  
  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: Use Math.abs() instead.
  
    1   │ - const·distance·=·value·>=·0·?·value·:·0·-·value;
      1 │ + const·distance·=·Math.abs(value);
    2 2 │

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if (offset > limit || offset < -limit) {}

code-block.js:1:5 lint/nursery/useMathAbs  FIXABLE  ━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━

  ⚠ This condition manually compares an absolute value with a limit.
  
  > 1 │ if (offset > limit || offset < -limit) {}
      │     ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
    2 │ 
  
  ℹ Math.abs() expresses this directly and avoids repeating the value for the positive and negative cases.
  
  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: Use Math.abs() instead.
  
    1   │ - if·(offset·>·limit·||·offset·<·-limit)·{}
      1 │ + if·(Math.abs(offset)·>·limit)·{}
    2 2 │

Valid

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const distance = Math.abs(value);
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if (Math.abs(offset) > limit) {}
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const size = count < 0n ? -count : count;