JS-Like-Numbers

Currently Supported for ES6 and higher

A small, fast JavaScript library for arbitrary-precision decimal arithmetic in javascript notation.

Install

$ npm install js-like-numbers

Usage

CommonJS:

const { op } = require('js-like-numbers')

ES module:

import { op } from 'js-like-numbers'

You need to pass to op a function with returned aritmetic operation or a number

const val = op(() => 1)
const val2 = op(() => (
    10000000000000000000000000000000000000000000
    + 55555555555555555555555
    + 111111111111.7891919191919191919191111111111111111
))

console.log(val.toString()) // 1
console.log(String(val2)) // 10000000000000000000055555555555666666666666.7891919191919191919191111111111111111

As you see You can work with any numbers in javascript notation.

Functions passed to op can also be fat functions:

const val = op(function f() {
    return 128931823123712839213 % 13213212312
})

console.log(val.valueOf()) // 449923381

Requirement: Your return statements MUST consists of arithmetic operations and include ONLY identifiers (variables) refering to BigNumbers as values:

const val = op(() => 1)
const result1 = op(() => (1 + val * 10) / val ** (2 + val)) // Is Correct

const incorrectVal = 1
const result2 = op(() => 1 + incorrectVal) // Error: You can use in return statement only variables initialized with BigNumber values

Requirement: op call body MUST contain only simple arithmetics (not related to BigNumbers), declarations of BigNumbers, or another op calls.

Requirement: Type castings of BigNumbers in op functions bodies MUST be performed using BigNumber.cast method.

const simpleNum = 2
const num1 = op(() => 1)
const result = op(function f() {
  const simpleMath = 16 + 2 / simpleNum
  const num2 = op(() => (num1 + num1) ** 2)
  const num3 = new BigNumber(simpleMath + '')
  // const bigNumberStringCasting = num3.toString() // This is not allowed, it can lead to logical errors.
  const validCasting = num3.cast('number')
  
  return num2 + 12 + num1 + (-num3) // 0
})

When you use exponentiation operation (**), be sure to pass as a second operand integer number between -1e+6 to 1e+6 inclusive.

const num1 = op(() => 2 ** 2) // 4
const num2 = op(() => 2 ** 2.1) // Error: Invalid exponent: Exponent must be a JavaScript number integer in range - -1e+6 to 1e+6 inclusive

When calculating modulo, result will be a value of first number modulo n, i.e. the integer remainder of dividing it by n.

The result will have the same sign as the first operand, and it will match that of JavaScript's % operator (within the limits of its precision) and BigDecimal's remainder method.

It will Throw if n is zero or otherwise invalid.

const num1 = op(() => 10 % 6) // 4
const num2 = op(() => -10 % 6) // -4
const num2 = op(() => -10 % -6) // -4

const num1 = op(() => -1 % 0.9) // -0.1
const num2 = op(() => 1 % -0.9) // 0.1
const num3 = op(() => -0 % 2) // -0

For comparison you have 5 methods on BigNumber instances:

• eq:

  const num1 = op(() => 1)
  const num2 = op(() => num1)
  console.log(num1.eq(num2)) // true
  console.log(num1.eq(1)) // true
  console.log(num1.eq('1')) // true

• gt:

  const num1 = op(() => 1)
  const num2 = op(() => num1 - 1)
  console.log(num1.gt(num2)) // true
  console.log(num1.gt(0)) // true
  console.log(num1.gt('0')) // true

• gte:

  const num1 = op(() => 1)
  console.log(num1.gte(num1)) // true
  console.log(num1.gte(1)) // true
  console.log(num1.gte('1')) // true

• lt:

  const num1 = op(() => 1)
  const num2 = op(() => num1 - 1)
  console.log(num1.lt(num2)) // false
  console.log(num1.lt(0)) // false
  console.log(num1.lt('0')) // false

• lte:

  const num1 = op(() => 1)
  const num2 = op(() => num1 - 1)
  console.log(num1.lte(num2)) // false
  console.log(num1.lte(1)) // true
  console.log(num1.lte('2')) // true

There are 2 additional methods, toFixed and toPrecision:

toFixed

Returns a string representing the value of this BigNumber in normal notation to a fixed number of decimal places.

Decimal places number must be integer from 0 to 1e+6 inclusive.

const num = op(() => 1.5451)
num.toFixed() // 1.5451 - same value in normal notation
num.toFixed(0) // 2 - rounded to closest integer
num.toFixed(1) // 1.5
num.toFixed(2) // 1.55
num.toFixed(3) // 1.545
num.toFixed(4) // 1.5451
num.toFixed(5) // 1.54510
num.toFixed(6) // 1.545100
num.toFixed(-1) // Error: Invalid argument decimalPlaces provided
num.toFixed(1e+6 + 1) // Error: Invalid argument decimalPlaces provided

toPrecision

Returns a string representing the value of this BigNumber to the specified number of significant digits.

Precision number must be integer from 1 to 1e+6 inclusive

const num = op(() => 1.5451)
num.toPrecision() // 1.5451 - same value in normal notation
num.toPrecision(1) // 2
num.toPrecision(2) // 1.5
num.toPrecision(3) // 1.55
num.toPrecision(4) // 1.545
num.toPrecision(5) // 1.5451
num.toPrecision(6) // 1.54510
num.toPrecision(-1) // Error: Invalid precision provided
num.toPrecision(1e+6 + 1) // Error: Invalid precision provided
num.toPrecision(0) // Error: Invalid precision provided

License

MIT