"convunits" Typescript Unit-Converter Library

Notes

The initial work was an extended version of the publicly available package https://www.npmjs.com/package/convert-units. At the time the goal was to quickly add some missing units in the existing quantities and, for example, added the "resistivity", the "slowness", the "pressureGradient" and the "volumeFlowRate" quantities.

Later, we rewrote the library to have the feature of recognizing a unit by its standard representation (unit key) but also by its non-standard representations (unit symbols), which can be added easily - in one place only, this library. This allows for multiple symbols to be recognized as one unit only ("feet", "foot", "ft" or "Ft" all are the same unit).

In this rewrite we also updated the tests to run them on build, guaranteeing aswell there are no duplicate occurrences of same symbol.

Additionally, as the main, feature, the unit definitions were extracted to JSON files, outside the code. This allows for the plugging in of a library in any other language (e.g. python, see /py folder.)

Development

To test locally from development in the directory, build first:

npm install
npm run build
npm link convunits

Make sure you have ts-node installed, if not: $ npm install -g ts-node

Test by playing around with the usage in tools/run.ts, then running it:

$ ts-node tools/run.ts

Usage

Import the Convert class and get a conversion result:

import { Convert } from 'convunits'
const result = new Convert(1).from('m').to('ft')

list all quantities can be found in "Definitions"

import { Definitions } from 'convunits'

To retrieve the unit key (standard symbol) for any supported unit symbol use the method "findStandardUnit". To retrieve the quantity for a given unit key (standard symbol) use the method "findQuantityBy".

import { findUnitStandard } from 'convunits'
import { findQuantityBy } from 'convunits'

const standardUnitSymbol = findUnitStandard('meter')
// standardUnitSymbol = 'm'
const quantity = findQuantityBy(standardUnitSymbol)

Release

If you want to release your changes in a new version: Bump version in package.json, commit and tag it.

git add package.json
git commit -m "1.0.1"
git push origin main

Create a tag via command line or UI.

git tag -a v1.0.1 -m '1.0.1'
git push origin --tags

Testing

Add the conversions you want to test in the respective .test.ts file inside /test/ directory Run the unit tests as: $ npm test

JSON to TS definitions

We have script for automating the conversion of JSON to TS definitions. One Typecript definition file will be generated in /ts/src/ts-definitions from each JSON file in /definitions: $ npm run json-to-ts This is integrated in the following command with formatting and tests: $ npm run all

Changing or adding new unit or quantity

For a new unit, go to the .json file of the quantity you are interested in. Add the unit as an entry of the "units" attribute, respecting the format. Add a test involving that unit in the unitttests.

For a new quantity, add the definition as .json file in /definitions directory, respecting the format. Make sure to add the newly created quantity in definitions.ts imports and exported array. Add tests involving that quantity as a separate test file, respecting the structure.

For rewriting concerned the definitions JSON files, use the migrateDifinitions.ts script in "/ts/tools/". Adapt it accordingly with source and target directories plus necessary logic from and to those JSON strcutures.

Finally run: $ npm run all