README.md

@beyondessential/arithmetic

Utility to evaluate BODMAS arithmetic formulas. It is an implementation of the shunting yard algorithm.

Installation

With yarn:

yarn add @beyondessential/arithmetic

With npm:

npm add @beyondessential/arithmetic

API

formulaText must be in BODMAS format.

runArithmetic(formulaText: string, values?: Record<string, string | number>): number

Usage example:

import { runArithmetic } from '@beyondessential/arithmetic';

const value = runArithmetic('(-1 + 2.5) / 3');
console.log(value); // 0.5

const valueWithVariable = runArithmetic('2 * four', {
  four: 4,
});
console.log(valueWithVariable); // 8

getVariables(formulaText: string): string[]

Usage example:

import { getVariables } from '@beyondessential/arithmetic';

const variables = getVariables('(-a * b - 1) / (c + 3)');
console.log(variables); // ['a', 'b', 'c']

formulaText operators

Note: All operators are case insensitive.

Operator	Example	Description
+	1 + 1	Addition
-	1 - 1	Subtraction
* or x	1 * 1 or 1 x 1	Multiplication
/	1 / 1	Division
()	1 / (1 + 1)	Brackets
-	-1	Unary minus
max	max(1, 2, 3)	Takes the maximum value of it's arguments. -Infinity if given none