useNumericSeparators

JavaScript (and super languages)

Summary

Diagnostic Category: lint/nursery/useNumericSeparators
This rule has a safe fix.
The default severity of this rule is information.
Sources:
- Same as unicorn/numeric-separators-style
- Same as unreadable_literal

Description

Enforce the use of numeric separators in numeric literals.

Enforces a convention of grouping digits using numeric separators. Long numbers can become difficult to read, so separating groups of digits with an underscore (_) improves code clarity. This rule also enforces proper usage of the numeric separator, by checking if the groups of digits are of the correct size.

Examples

Invalid

1
var a = 1234567890;

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

  ℹ Long numeric literal lacks separators.
  
  > 1 │ var a = 1234567890;
      │         ^^^^^^^^^^
    2 │ 
  
  ℹ Adding separators helps improve readability and clarity for long numbers.
  
  ℹ Safe fix: Add numeric separators.
  
    1   │ - var·a·=·1234567890;
      1 │ + var·a·=·1_234_567_890;
    2 2 │

1
var a = -999_99;

code-block.js:1:10 lint/nursery/useNumericSeparators  FIXABLE  ━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━

  ℹ Inconsistent grouping of digits in numeric literal.
  
  > 1 │ var a = -999_99;
      │          ^^^^^^
    2 │ 
  
  ℹ Numbers with inconsistently placed separators can be misleading or confusing.
  
  ℹ Safe fix: Use consistent numeric separator grouping.
  
    1   │ - var·a·=·-999_99;
      1 │ + var·a·=·-99_999;
    2 2 │

1
var a = 0.1234567;

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

  ℹ Long numeric literal lacks separators.
  
  > 1 │ var a = 0.1234567;
      │         ^^^^^^^^^
    2 │ 
  
  ℹ Adding separators helps improve readability and clarity for long numbers.
  
  ℹ Safe fix: Add numeric separators.
  
    1   │ - var·a·=·0.1234567;
      1 │ + var·a·=·0.123_456_7;
    2 2 │

1
var a = 0b11001100;

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

  ℹ Long numeric literal lacks separators.
  
  > 1 │ var a = 0b11001100;
      │         ^^^^^^^^^^
    2 │ 
  
  ℹ Adding separators helps improve readability and clarity for long numbers.
  
  ℹ Safe fix: Add numeric separators.
  
    1   │ - var·a·=·0b11001100;
      1 │ + var·a·=·0b1100_1100;
    2 2 │

Valid

1
var a = 1_234_567_890;

1
var a = -99_999;

1
var a = 0.123_456_7;

1
var a = 0b1100_1100;

How to configure

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