unicorn/numeric-separators-style Style ​
What it does ​
Enforces a convention of grouping digits using numeric separators.
Why is this bad? ​
Long numbers can become really hard to read, so cutting it into groups of digits, separated with a _, is important to keep your code clear. This rule also enforces a proper usage of the numeric separator, by checking if the groups of digits are of the correct size.
Examples ​
Examples of incorrect code for this rule:
javascript
const invalid = [
1_23_4444,
1_234.56789,
0xAB_C_D_EF,
0b10_00_1111,
0o1_0_44_21,
1_294_28771_2n,
];Examples of correct code for this rule:
javascript
const valid = [
1_234_567,
1_234.567_89,
0xAB_CD_EF,
0b1000_1111,
0o10_4421,
1_294_287_712n,
];Configuration ​
This rule accepts a configuration object with the following properties:
binary ​
type: object
Configuration for binary literals (e.g. 0b1010_0001 and bigint variants). Controls how digits are grouped and when separators are applied.
binary.groupLength ​
type: integer
The number of digits per group when inserting numeric separators. For example, a groupLength of 3 formats 1234567 as 1_234_567.
binary.minimumDigits ​
type: integer
The minimum number of digits required before grouping is applied. Values with fewer digits than this threshold will not be grouped.
hexadecimal ​
type: object
Configuration for hexadecimal literals (e.g. 0xAB_CD, 0Xab_cd, and bigint variants). Controls how digits are grouped and when separators are applied.
hexadecimal.groupLength ​
type: integer
The number of digits per group when inserting numeric separators. For example, a groupLength of 3 formats 1234567 as 1_234_567.
hexadecimal.minimumDigits ​
type: integer
The minimum number of digits required before grouping is applied. Values with fewer digits than this threshold will not be grouped.
number ​
type: object
Configuration for decimal numbers (integers, fraction parts, and exponents). Controls how digits are grouped and when separators are applied.
number.groupLength ​
type: integer
The number of digits per group when inserting numeric separators. For example, a groupLength of 3 formats 1234567 as 1_234_567.
number.minimumDigits ​
type: integer
The minimum number of digits required before grouping is applied. Values with fewer digits than this threshold will not be grouped.
octal ​
type: object
Configuration for octal literals (e.g. 0o1234_5670 and bigint variants). Controls how digits are grouped and when separators are applied.
octal.groupLength ​
type: integer
The number of digits per group when inserting numeric separators. For example, a groupLength of 3 formats 1234567 as 1_234_567.
octal.minimumDigits ​
type: integer
The minimum number of digits required before grouping is applied. Values with fewer digits than this threshold will not be grouped.
onlyIfContainsSeparator ​
type: boolean
default: false
Only enforce the rule when the numeric literal already contains a separator (_).
When true, numbers without separators are left as-is; when false (default), grouping will be enforced for eligible numbers even if they don't include separators yet.
How to use ​
To enable this rule in the CLI or using the config file, you can use:
bash
oxlint --deny unicorn/numeric-separators-stylejson
{
"rules": {
"unicorn/numeric-separators-style": "error"
}
}