#prefer-math-constants

#Configuration

import { defineConfig, unicornPlugin } from '@rslint/core';

export default defineConfig([
  unicornPlugin.configs.recommended,
  {
    rules: {
      'unicorn/prefer-math-constants': 'error',
    },
  },
]);

#Rule details

Prefer named Math constants when a decimal literal matches a rounded or truncated value. The rule checks Math.PI, Math.E, Math.LN2, Math.LN10, Math.LOG2E, Math.LOG10E, Math.SQRT2, and Math.SQRT1_2.

The minimum number of fractional digits is two for Math.PI, three for Math.E, and four for the other constants. The rule counts the written digits and ignores numeric separators. It skips exponential notation, non-computed property names, and TypeScript literal types.

Replacing an approximation can change a calculation, so the rule offers an editor suggestion for the user to apply.

#Incorrect

const area = 3.14 * radius ** 2;
const growth = amount * 2.718;
const diagonal = side * 1.4142;

#Correct

const area = Math.PI * radius ** 2;
const growth = amount * Math.E;
const diagonal = side * Math.SQRT2;

#Options

This rule has no options.

#Differences from upstream

• Rslint adds whitespace when a suggestion would join adjacent tokens. For example, return.6931 becomes return Math.LN2.
• If a local binding shadows Math or languageOptions.globals disables it, Rslint reports the literal and withholds the suggestion.
• Rslint withholds suggestions in places where TypeScript requires a literal or constant expression. This includes const assertions such as 3.14 as const, enum initializers that determine an implicit member value or belong to a const enum, declarations such as declare const angle = 3.14, and computed property names in interfaces.

#Original documentation

• Upstream documentation
• Upstream source