vend-number

A collection of utility methods for floating point Number operations

vend-number is a vend-flavoured wrapper for BigNumber.js.

Instead of constructing BigNumber objects from your numbers and performing operations on them within your app, this module provides a set of simplified math utilities that take simple Number or String types, and use BigNumber operations for accuracy behind the scenes.

API

VendNumber is an extension of the BigNumber class.

import VendNumber from 'vend-number'

const num = new VendNumber('123.456')
num.round(2) // '123.46'
num instanceof BigNumber // true

There is a shortcut method of construction in VendNumber.vn:

import VendNumber, { vn } from 'vend-number'

const num = vn(123.456)
num.round(2) // '123.46'
num instanceof VendNumber // true

Math operations

The following static methods can take any number of values and perform the operation on each of them in the specified order.

Add a list of values

VendNumber.add(1, 2, 3) // 1 + 2 + 3 = 6

Subtract a list of values

VendNumber.subtract(2, 1) // 2 - 1 = 1

Multiply a list of values

VendNumber.multiply(2, 2) // 2 * 2 = 4

Divide a list of values

VendNumber.divide(10, 2) // 10 / 2 = 5

Keep in mind when using the VendNumber math functions that when performing multiple calculations you will need to make sure the execution order is correct.

Native JS will execute in order of BEDMAS automatically, whereas with these methods, you have to make sure of this manually.

E.g.

4 * 5 + 3 // returns 23

multiply(4, add(5, 3)) // returns 32

You need to take into account the order in which the functions will be executed, so in this case it should be:

add(3, multiply(4, 5)) // returns 23

Rounding and formatting

Round a value to a specified number of decimal points. The default rounding mode is ROUND_HALF_UP, the 'Round Half Away From Zero' tie-breaking rule.

VendNumber.round(5.545333, 2) // "5.55"

Rounding modes

You can specify any of the Big Number rounding modes to the round function. These are available via VendNumber.ROUNDING_METHODS.

import VendNumber, { ROUNDING_MODES } from 'vend-number'

VendNumber.round(5.545333, 2, ROUNDING_MODES.ROUND_DOWN) // "5.54"

isFinite

A static equivalent to BigNumber.isFinite that reports false for non-numeric values.

VendNumber.isFinite(null) // false
VendNumber.isFinite('') // false
VendNumber.isFinite(Infinity) // false

VendNumber.isFinite(0) // true
VendNumber.isFinite(Number.MAX_VALUE) // true
VendNumber.isFinite('-123.456') // true

sumBy

Calculates the sum of all items in a collection based on a property name.

Accepts the following parameters:

• Array an array of items to loop through.
• String a property name to sum by.
• Number an optional decimal points number to round the sum value to (defaults to 2 d.p.).

Example:

VendNumber.sumBy([], '') // 0.00
VendNumber.sumBy([{ a: 1 }, { a: 2 }], 'a') // 3.00
VendNumber.sumBy([{ a: 1.4222 }, { a: 2.1115 }], 'a', 3) // 3.534

Contributing

Test

yarn test

License

MIT © Vend