Safe Units
Safe Units is a type safe library for using units of measurement in TypeScript. Safe Units provides an implementation of an SI based unit system but is flexible enough to allow users to create their own unit systems which can be independent or can interoperate with the built-in units. Users can also make unit systems for any numeric type they'd like not just the JavaScript number type. This library requires TypeScript 3.2 or higher.
import { Length, Measure, meters, seconds, Time, Velocity } from "safe-units";
const length: Length = Measure.of(30, meters);
const time: Time = Measure.of(15, seconds);
const velocity: Velocity = length.over(time);
console.log(length.toString()); // 30 m
console.log(time.toString()); // 15 s
console.log(velocity.toString()); // 2 m * s^-1
const error: Velocity = length.times(time);
// ERROR: A measure of m*s isn't assignable to a measure of m/s.Features
Prerequisites
Safe units is written in TypeScript and should be consumed by TypeScript users to take full advantage of what it provides. In addition you will need the following:
- TypeScript 3.2 or later
- Strict null checks enabled for your project
Installation
npm install safe-units
or
yarn add safe-units
Examples
Unit arithmetic
import { bars, kilograms, Measure, meters, milli, seconds } from "safe-units";
const width = Measure.of(3, meters);
const height = Measure.of(4, meters);
const area = width.times(height).scale(0.5);
const hypot = Measure.sqrt(width.squared().plus(height.squared())); // 5 m
const mass = Measure.of(30, kilograms);
const mps2 = meters.per(seconds.squared());
const acceleration = Measure.of(9.8, mps2);
const force = mass.times(acceleration); // 294 N
const pressure = force.over(area); // 49 Pa
const maxPressure = Measure.of(0.5, milli(bars)); // 0.5 mbar
pressure.lt(maxPressure) // trueType errors
import { Force, Length, Measure, meters, seconds, Time } from "safe-units";
const length: Length = Measure.of(10, meters);
const time: Time = Measure.of(10, seconds);
length.plus(time);
// ERROR: Measures of different units cannot be added
length.minus(time);
// ERROR: Measures of different units cannot be subtracted
const force: Force = length.over(time);
// ERROR: Measure of m/s is not assignable to measure of kg*m/s^2
const root = Measure.sqrt(length);
// ERROR: Can't take sqrt of measure of m since it's not a perfect squareNaming units
import { days, Measure, miles, speedOfLight, yards } from "safe-units";
const furlongs = Measure.of(220, yards, "fur");
console.log(Measure.of(8, furlongs).in(miles)); // 1 mi
console.log(Measure.of(1, miles).in(furlongs)); // 8 fur
const fortnights = Measure.of(14, days, "ftn");
const megaFurlongsPerMicroFortnight = mega(furlongs)
.per(micro(fortnights))
.withSymbol("Mfur/ยตftn");
console.log(speedOfLight.in(megaFurlongsPerMicroFortnight)); // 1.8026174997852542 Mfur/ยตftnDeriving quantities
import { Acceleration, Measure, meters, seconds, Time } from "safe-units";
const Jerk = Acceleration.over(Time);
type Jerk = typeof Jerk;
const mps2 = meters.per(seconds.squared());
const acceleration = Measure.of(9.8, mps2);
const jerk: Jerk = acceleration.over(Measure.of(2, seconds));
console.log(jerk.toString()); // 4.9 m * s^-3Defining dimensions
import { Area, Measure, minutes, seconds, Time } from "safe-units";
const frames = Measure.dimension("frames");
const Frames = frames;
type Frames = typeof frames;
const FrameRate = Frames.over(Time);
type FrameRate = typeof FrameRate;
const fps: FrameRate = frames.per(seconds).withSymbol("fps");
const minFrameRate = Measure.of(60, fps);
const measuredFrames = Measure.of(8000, frames);
const elapsedTime = Measure.of(2, minutes);
const measuredFps: FrameRate = measuredFrames.over(elapsedTime);
if (measuredFps.lt(minFrameRate)) {
// Optimize
}