Numeric types for JavaScript

This library contains implementations of useful numeric types for JavaScript and TypeScript.

npm install numeric-types

Features and status

This is currently an early release.

• Rounding modes: up, down, half down, half even, half up, floor and ceiling
• Decimal number representation
  • Decimal on top of number with limited precision of 15 digits
  • BigDecimal for more precise numbers, with up to Number.MAX_SAFE_INTEGER digits
  • Basic math operations: add, subtract, multiply, divide
• Integer representation
  • Integer for integers between Number.MIN_SAFE_INTEGER and Number.MAX_SAFE_INTEGER
  • BigInteger for large integers

API

In this library all numeric types are immutable, so functions always return a new instance. Each numeric type provides a limited API to support their creation and basic use.

Operations on the number types is provided as separate functions that can be imported. This design is to allow the library to take advantage of tree-shaking.

• static NumericType.fromNumber(value: number): NumericType

  Create an instance of the numeric type from a regular JavaScript number.

• static NumericType.parse(value: string): NumericType

  Create an instance of the numeric type from a string.

• numericType.toString(): string

  Turn the numeric type into a string representation supported by fromString.

MathContext and rounding

This library uses a class named MathContext to support operations such as setting the scale or precision and rounding a number.

import { MathContext, RoundingMode } from 'numeric-types';
 
// Create a context that requests 2 digits after the decimal using Half Up rounding
const contextWithScale = MathContext.ofScale(2, RoundingMode.HalfUp);
 
// Context that requests at max 10 digits of precision
const contextWithPrecision = MathContext.ofPrecision(10, RoundingMode.Ceiling);

Rounding modes

• RoundingMode.Down - Round towards zero.
• RoundingMode.Up - Round away from zero.
• RoundingMode.HalfDown - Round towards the nearest neighbor, but if in the middle round towards zero.
• RoundingMode.HalfEven - Round towards the nearest neighbor, but if in the middle round towards the even neighbor.
• RoundingMode.HalfUp - Round towards the nearest neighbor, but if in the middle round away from zero.
• RoundingMode.Floor - Round towards negative infinity.
• RoundingMode.Ceiling - Round towards positive infinity.
• RoundingMode.Unnecessary - Do not round, instead throw an error if rounding is required.

Type: Decimal

Decimal is an implementation of a numeric type that avoids the rounding errors common with floating point numbers. There are two versions, Decimal and BigDecimal where Decimal is limited to safely handling 15 digits and BigDecimal can handle up to Number.MAX_SAFE_INTEGER digits:

import { Decimal, multiply } from 'numeric-types/decimal';
 
const a = Decimal.fromNumber(0.1);
const b = Decimal.parse('12');
 
const ab = multiply(a, b);
console.log(ab.toString());

Types are available for TypeScript:

import { AbstractDecimal, Decimal } from 'numeric-types/decimal';
 
const decimal: AbstractDecimal<any> = Decimal.fromNumber(0.1);

Operations

These operations are available from numeric-types/decimal. Import them separately like:

import { operationHere, anotherOperation } from 'numeric-types/decimal';
 
const { operationHere, anotherOperation } = require('numeric-types/decimal');

• compare(a: DecimalType, b: DecimalType): -1 | 0 | 1

  Compare two decimal numbers. This method will return 0 if the numbers are the same, -1 if a is less than b and 1 if a is greater than b.

• isEqual(a: DecimalType, b: DecimalType): boolean

  Get if two decimal numbers are equal.

• isLessThan(a: DecimalType, b: DecimalType): boolean

  Get if the decimal number a is less than the number b.

• isLessThanOrEqual(a: DecimalType, b: DecimalType): boolean

  Get if the decimal number a is less than or equal to the number b.

• isGreaterThan(a: DecimalType, b: DecimalType): boolean

  Get if the decimal number a is greater than the number b.

• isGreaterThanOrEqual(a: DecimalType, b: DecimalType): boolean

  Get if the decimal number a is greater than or equal to the number b.

• toString(a: DecimalType): string

  Turn a decimal numbers into its string representation.

• scale(a: DecimalType, context: MathContext): DecimalType

  Scale the given decimal number according to the specified context.

• round(a: DecimalType, roundingMode?: RoundingMode): DecimalType

  Round the given decimal number. If the rounding mode is not specified RoundingMode.HalfUp is used. This is equivalent to calling scale with MathContext.ofScale(0, roundingMode).

• add(a: DecimalType, b: DecimalType, context?: MathContext): DecimalType

  Add two decimal numbers together, optionally specifying a context to be used to adjust the scale of the result.

• subtract(a: DecimalType, b: DecimalType, context?: MathContext): DecimalType

  Subtract a decimal number b from the number a. Optionally specify a context to be used to adjust the scale of the result.

• multiply(a: DecimalType, b: DecimalType, context?: MathContext): DecimalType

  Multiply two decimal numbers together. Optionally specify a context to be used to adjust the scale of the result.

• divide(a: DecimalType, b: DecimalType, context: MathContext): DecimalType

  Divide a decimal number b from the number a. A context is required to determine the scale and how to round things.

Type: Integer

Integer is an implementation of a whole number. There are currently two versions available, Integer which is limited to the range of number and BigInteger which is can represent larger numbers.

import { Integer, multiply } from 'numeric-types/integer';
 
const a = Integer.fromNumber(20);
const b = Integer.parse('40');
 
const ab = multiply(a, b);
console.log(ab.toString());

Types are available for TypeScript:

import { AbstractInteger, Integer } from 'numeric-types/integer';
 
const integer: AbstractInteger<any> = Integer.fromNumber(1);

Operations

These operations are available from numeric-types/integer. Import them separately like:

import { operationHere, anotherOperation } from 'numeric-types/integer';
 
const { operationHere, anotherOperation } = require('numeric-types/integer');

• compare(a: IntegerType, b: IntegerType): -1 | 0 | 1

  Compare two integers. This method will return 0 if the numbers are the same, -1 if a is less than b and 1 if a is greater than b.

• isEqual(a: IntegerType, b: IntegerType): boolean

  Get if two integers are equal.

• isLessThan(a: IntegerType, b: IntegerType): boolean

  Get if the integer a is less than the number b.

• isLessThanOrEqual(a: IntegerType, b: IntegerType): boolean

  Get if the integer a is less than or equal to the number b.

• isGreaterThan(a: IntegerType, b: IntegerType): boolean

  Get if the integer a is greater than the number b.

• isGreaterThanOrEqual(a: IntegerType, b: IntegerType): boolean

  Get if the integer a is greater than or equal to the number b.

• toString(a: IntegerType): string

  Turn a integers into its string representation.

• add(a: IntegerType, b: IntegerType): IntegerType

  Add two integers together.

• subtract(a: IntegerType, b: IntegerType): IntegerType

  Subtract b from a

• multiply(a: IntegerType, b: IntegerType): IntegerType

  Multiply two integers together.

• divide(a: IntegerType, b: IntegerType): IntegerType

  Divide a by the divisor b.