decimal.js

@usenarrator/plugin-decimal Money code often uses decimal.js to avoid floating point errors. Without help, a chain like new Decimal(a).times(b).plus(c) reads as a series of method calls. The decimal plugin reads it as arithmetic, and reads comparisons as comparisons, including their negations. This plugin is also the worked example in Writing a plugin.

import { decimal } from "@usenarrator/plugin-decimal";

typescript({ parser: oxcParser, plugins: [decimal()] });

Examples

Arithmetic chains read left to right

const subtotal = new Decimal(price).times(quantity);
const total = subtotal.plus(shipping).minus(discount);
const perSeat = total.dividedBy(seats).toDecimalPlaces(2);

English

Let subtotal be price times quantity.
Let total be subtotal plus shipping minus discount.
Let per seat be total divided by seats rounded to 2 decimal places.

Comparisons and their negations

if (new Decimal(balance).lte(0)) suspendAccount(account);
if (!new Decimal(balance).lte(0)) resumeAccount(account);
if (!refund.isZero()) issueRefund(refund);

English

If balance is at most 0, suspend account (account).
If balance is more than 0, resume account (account).
If refund is not zero, issue refund (refund).

Without the plugin, the same comparison reads like this:

Without the plugin

if (new Decimal(balance).lte(0)) suspendAccount(account);

English

If there is a new decimal (balance)'s lte (0), suspend account (account).

What it covers

new Decimal(x) reads as x.
Arithmetic: plus and add, minus and sub, times and mul, div and dividedBy, toDecimalPlaces, toNumber. add is only claimed on a new Decimal(...) receiver, so set.add(x) is unaffected.
Conditions: lt, lte, gt, gte, eq, equals, isZero, isNegative, isPositive.

Translating

The English phrasebook is exported as decimalEn and typed as DecimalPhrases.

Plugins

Validation

Data

Servers

Frontend

Payments, auth & AI

Jobs

Effect & testing

Examples

What it covers

Translating

​Examples

​What it covers

​Translating

Examples

What it covers

Translating