prefer-number-properties.md

prefer-number-properties

📝 Prefer Number static properties over global ones.

💼 This rule is enabled in the following configs: ✅ recommended, ☑️ unopinionated.

🔧💡 This rule is automatically fixable by the --fix CLI option and manually fixable by editor suggestions.

ECMAScript 2015 moved globals onto the Number constructor for consistency and to slightly improve them. This rule enforces their usage to limit the usage of globals:

• Number.parseInt() over parseInt() (fixable)
• Number.parseFloat() over parseFloat() (fixable)
• Number.isNaN() over isNaN() (they have slightly different behavior)
• Number.isFinite() over isFinite() (they have slightly different behavior)
• Number.NaN over NaN (fixable)
• Number.POSITIVE_INFINITY over Infinity (fixable)
• Number.NEGATIVE_INFINITY over -Infinity (fixable)

Examples

// ❌
const foo = parseInt('10', 2);

// ✅
const foo = Number.parseInt('10', 2);

// ❌
const foo = parseFloat('10.5');

// ✅
const foo = Number.parseFloat('10.5');

// ❌
const foo = isNaN(10);

// ✅
const foo = Number.isNaN(10);

// ❌
const foo = isFinite(10);

// ✅
const foo = Number.isFinite(10);

// ❌
if (Object.is(foo, NaN)) {}

// ✅
if (Object.is(foo, Number.NaN)) {}

// ✅
const foo = Number.parseInt('10', 2);

// ✅
const {parseInt} = Number;
const foo = parseInt('10', 2);

// ✅
const isPositiveZero = value => value === 0 && 1 / value === Number.POSITIVE_INFINITY;

// ✅
const isNegativeZero = value => value === 0 && 1 / value === Number.NEGATIVE_INFINITY;

// ✅
const isPositiveZero = value => value === 0 && 1 / value === Infinity;

// ✅
const isNegativeZero = value => value === 0 && 1 / value === -Infinity;

Options

Type: object

checkInfinity

Type: boolean
Default: false

Pass checkInfinity: true to enable check on Infinity.

/* eslint unicorn/prefer-number-properties: ["error", {"checkInfinity": true}] */

// ❌
const foo = Infinity;

// ✅
const foo = Number.POSITIVE_INFINITY;

// ❌
const foo = -Infinity;

// ✅
const foo = Number.NEGATIVE_INFINITY;

checkNaN

Type: boolean
Default: true

Pass checkNaN: false to disable check on NaN.

/* eslint unicorn/prefer-number-properties: ["error", {"checkNaN": false}] */

// ✅
const foo = NaN;

// ✅
const foo = -NaN;