Annotate

README.md

@@ -31,6 +31,79 @@ measure(10000) // 10_000 ||  "1 ha"
 measure(1000000) // 1_000_000 ||  "1 km²"
 ```
 
+## Units
+
+### SI prefixes
+
+Meters (normal, square and cubic), grams and litres are prefixable with [SI prefixes](https://en.wikipedia.org/wiki/Metric_prefix#List_of_SI_prefixes). Examples:
+
+| Key | Unit             | Value           |
+| --- | ---------------- | --------------- |
+| km  | kilometre        | 1 \* 1000       |
+| cm  | centimetre       | 1 / 100         |
+| ml  | mililitre        | 1 / 1000        |
+| km2 | square kilometre | 1 _ 1000 _ 1000 |
+
+### Length
+
+| Key | Name          | Value           |
+| --- | ------------- | --------------- |
+| m   | Meter (meter) | 1               |
+| M   | Nautical Mile | Metre \* 1852   |
+| in  | Inch          | Foot / 12       |
+| ft  | Foot          | Yard / 3        |
+| yd  | Yard          | Metre \* 0.9144 |
+| ch  | Chain         | Yard \* 22      |
+| fur | Furlong       | Chain \* 10     |
+| mi  | Mile          | Furlong \* 8    |
+| lea | League        | Mile \* 3       |
+
+### Area
+
+Square length units can be used to measure area, i.e. "m2".
+
+| Key | Name    | Value             |
+| --- | ------- | ----------------- |
+| a   | Are     | Metre \*_ 2 _ 100 |
+| ha  | Hectare | Are \* 100        |
+| ac  | Acre    | Yard \*_ 2 _ 4840 |
+
+### Volume
+
+Cubic length units can be used to measure volume, i.e. "m3".
+
+I'm not sure how imperial volume units "really" work (in practise), so create an issue or PR to fix anything that is a miss.
+
+| Key   | Name                   | Value                      |
+| ----- | ---------------------- | -------------------------- |
+| l     | Litre                  | Metre \*\* 3 / 1000        |
+| pint  | Pint (Imperial)        | Litre \* 0.568             |
+| gal   | Gallon (American)      | Inch \*\* 3 / 231          |
+| qt    | Quart (American)       | Gallon / 4                 |
+| pt    | Pint (American)        | Gallon / 8                 |
+| gi    | Gill (American)        | Gallon / 32                |
+| fl oz | Fluid Ounce (American) | Gallon / 128               |
+| peck  | Peck                   | Litre \* 8.809_768         |
+| bu    | Bushel                 | Litre \* 35.239_070_166_88 |
+
+### Mass (weight)
+
+| Key     | Name                           | Value              |
+| ------- | ------------------------------ | ------------------ |
+| kg      | Kilogram                       | 1                  |
+| g       | Gram                           | Kilogram / 1000    |
+| lb      | Pound                          | Gram \* 453.592_37 |
+| t       | Tonne (Metric Ton)             | Kilogram \* 1000   |
+| ton     | American Ton (short)           | Pound \* 2000      |
+| longton | Imperial Ton (long)            | Pound \* 2240      |
+| cwt     | American Hundredweight (short) | Pound \* 100       |
+| longcwt | Imperial Hundredweight (long)  | Pound \* 112       |
+| qr      | Quarter                        | Pound \* 28        |
+| st      | Stone                          | Pound \* 14        |
+| oz      | Ounce                          | Pound / 16         |
+| dr      | Drachm                         | Pound / 256        |
+| gr      | Grain                          | Pound / 7000       |
+
 ## Roadmap
 
 - [Suggest units](https://stackoverflow.com/questions/56947641/generating-union-string-type)

__tests__/index.ts

@@ -262,10 +262,10 @@ describe('Volume units', () => {
     expect(String(res)).toBe('1 pt')
   })
 
-  test('pt', () => {
+  test('pint', () => {
     const measure = new Measure(0.000568261)
-    const res = measure.to('pint_long')
-    expect(String(res)).toBe('1 pt')
+    const res = measure.to('pint')
+    expect(String(res)).toBe('1 pint')
   })
 
   test('fl oz', () => {
@@ -301,16 +301,16 @@ describe('Weight units', () => {
     const res = measure.to('t')
     expect(String(res)).toBe('1 t')
   })
-  test('t US', () => {
+  test('ton', () => {
     const measure = new Measure(907.185)
-    const res = measure.to('ton_short')
-    expect(String(res)).toBe('1 t')
+    const res = measure.to('ton')
+    expect(String(res)).toBe('1 ton')
   })
 
-  test('t UK', () => {
+  test('longton', () => {
     const measure = new Measure(1016.05)
-    const res = measure.to('ton_long')
-    expect(String(res)).toBe('1 t')
+    const res = measure.to('longton')
+    expect(String(res)).toBe('1 longton')
   })
 
   test('lb', () => {
@@ -349,15 +349,15 @@ describe('Weight units', () => {
     expect(String(res)).toBe('1 qr')
   })
 
-  test('cwt UK', () => {
+  test('longcwt', () => {
     const measure = new Measure(50.8)
-    const res = measure.to('hundredweight_long')
-    expect(String(res)).toBe('1 cwt')
+    const res = measure.to('longcwt')
+    expect(String(res)).toBe('1 longcwt')
   })
 
-  test('cwt US', () => {
+  test('cwt', () => {
     const measure = new Measure(45.36)
-    const res = measure.to('hundredweight_short')
+    const res = measure.to('cwt')
     expect(String(res)).toBe('1 cwt')
   })
 })

src/findUnit.ts

@@ -1,11 +1,11 @@
-import units from './units'
+import units, { UnitKey } from './units'
 import siPrefixes from './SIPrefixes'
 
 const SQUARE_SYMBOLS = ['²', '2']
 const CUBE_SYMBOLS = ['³', '3']
 
 const findUnit = (
-  unitString: string
+  unitString: UnitKey
 ): {
   unit: string
   prefix: string

src/measure.ts

@@ -1,9 +1,14 @@
-// import siPrefixes from './SIPrefixes'
-// import units, { LENGTH } from './units'
 import findUnit from './findUnit'
+import { UnitKey } from './units'
 
 /**
- * Measure space in meters.
+ * Measure of value with unit.
+ * Length, area, volume and mass units.
+ * SI, metric and imperial units.
+ * Squared and cubed length units (m2, m3, km2, m3, ft3, mi2).
+ * SI prefixes (da, h, k, M, G, T, P, E, Z, Y, d, c, m, μ, n, p, f, a, z, y) for (m, m2, m3, l, g) i.e. (km2, kg, cm, ml).
+ *
+ * @returns {Number|String} `Measure.valueOf(): Number` or `Measure.toString(): String` depending on context
  */
 export default class Measure extends Number implements Number {
   public precision = 12
@@ -14,22 +19,28 @@ export default class Measure extends Number implements Number {
   public suffix = ''
   public round = 2
 
-  constructor(value: number | string | Measure, unitString?: string) {
+  /**
+   * @param value value/quantity of unit
+   * @param unitKey key representation of unit
+   */
+  constructor(value: number | string | Measure, unitKey?: UnitKey) {
     super(value)
-    if (unitString) {
-      const { unit, prefix, suffix, ratio } = findUnit(unitString.trim())
+    if (unitKey) {
+      const { unit, prefix, suffix, ratio } = findUnit(unitKey)
       this.symbol = unit
       this.prefix = prefix
       this.suffix = suffix
       this.ratio = 1 / ratio
     }
   }
 
-  public to = (unitString: string): Measure => {
-    // check if squared or cubed
-    let trimmed = unitString.trim()
-
-    const { unit, prefix, suffix, ratio } = findUnit(trimmed)
+  /**
+   * Convert Measure to another Measure with different Unit.
+   *
+   * @param unitKey key representation of unit
+   */
+  public to = (unitKey: UnitKey): Measure => {
+    const { unit, prefix, suffix, ratio } = findUnit(unitKey)
     this.symbol = unit
     this.prefix = prefix
     this.suffix = suffix
@@ -41,6 +52,12 @@ export default class Measure extends Number implements Number {
     return this.clone(newValue)
   }
 
+  /**
+   * Create a copy of of Measure with new value.
+   * Why? Because value of Number that we extend is immutable.
+   *
+   * @param value new value
+   */
   public clone(value: number) {
     const measure = new Measure(value)
     measure.ratio = this.ratio

src/measureSelector.ts

@@ -1,5 +1,6 @@
 import findUnit from './findUnit'
 import Measure from './measure'
+import { UnitKey } from './units'
 
 const toMeasure = (
   {
@@ -14,18 +15,29 @@ const toMeasure = (
   value: number
 ) => {
   const unitString = prefix + unit + suffix
-  return new Measure(value).to(unitString)
+  return new Measure(value).to(<UnitKey>unitString)
 }
 
-const createMeasureSelector = (...args: string[]) => {
-  const units = args.map(findUnit).sort((a, b) => b.ratio - a.ratio)
+/**
+ * Creates a function that finds best looking unit for value from a list of provided units.
+ * @param unitKeys an Array of unit identifiers.
+ * @returns {(value: number) => Measure} Finds best looking unit for pretty printing and returns Measure with it.
+ */
+const createMeasureSelector = (...unitKeys: UnitKey[]) => {
+  const units = unitKeys.map(findUnit).sort((a, b) => b.ratio - a.ratio)
 
-  return function(value: number) {
+  /**
+   * Finds best looking unit for pretty printing and returns Measure with it.
+   *
+   * @param value quantity/value of measure.
+   * @returns {Measure} new Measure(value, bestLookingUnit)
+   */
+  const finder = (value: number) => {
     const found = units.reduce(
       // find smallest unit larger than 1
       (previousUnit, currentUnit) => {
-        const currentQuantity = Number(toMeasure(currentUnit, value)) //currentUnit.quantity(value)
-        const previousQuantity = Number(toMeasure(previousUnit, value)) // previousUnit.quantity(value)
+        const currentQuantity = Number(toMeasure(currentUnit, value))
+        const previousQuantity = Number(toMeasure(previousUnit, value))
 
         return previousQuantity < 1 || currentQuantity < previousQuantity
           ? currentUnit
@@ -41,6 +53,8 @@ const createMeasureSelector = (...args: string[]) => {
       return foundMeasure
     }
   }
+
+  return finder
 }
 
 export default createMeasureSelector