@freemework/decimal.bignumberjs

Freemework

FDecimal is a data type for storing decimal values and manipulate its via mathematical functions according infinite-precision arithmetic. It should be used when it is important to preserve exact precision, for example with monetary data.

Problems of JavaScript IEEE 754 floating point numbers.

Approximation

const totalMoney = 600.9;
const pricePerItem = 200.3;
const totalSpent = pricePerItem * 3;

console.log(totalMoney === totalSpent); // false (while expected true)
console.log(totalSpent); // 600.9000000000001

Digits limit

const left = parseInt("123456789012345678901234567890");
const right = parseInt("1");
const result = left + right;
console.log(result); // 1.2345678901234568e+29 (while expected 123456789012345678901234567891)

Examples

You can see a lot of examples in unit tests. Here we show some points only.

Avoid approximation

const { FDecimal } = require("@freemework/decimal.bignumberjs");

const totalMoney = FDecimal.fromFloat(600.90, 2);
const pricePerItem = FDecimal.fromFloat(200.30, 2);
const buyItems = FDecimal.fromInt(3);
const totalSpent = FDecimal.multiply(pricePerItem, buyItems);

console.log(FDecimal.equalsTo(totalMoney, totalSpent)); // true
console.log(FDecimal.toString(totalSpent));             // 600.9

Avoid digits limit

import { FDecimal } from "@freemework/decimal.bignumberjs";

const left = "123456789012345678901234567890";
const right = "1";
const result = FDecimal.plus(left, right);
console.log(result); // 123456789012345678901234567891

Documentation

• Getting Started
• Examples
• Overview

Build

npm install
npm run build

This will build the library and put them in the folder .dist

Test

To execute tests for the library, install the project dependencies once:

npm install
npm run build
npm run test