Added in function to get prefixes and units. Address #48, #14

README.md

@@ -99,6 +99,19 @@ Qty.parse('foo') // => null
 Qty.getKinds(); // => Array of names of every well-known kind of units
 ```
 
+### Available unit names by category
+
+```javascript
+Qty.getUnits(); // => Object of unit arrays of every well-known kind of units
+// Can be optionally restricted to only one kind
+Qty.getUnits("length"); // => Array of all units of type length
+```
+### Available well-known prefixes
+
+```javascript
+Qty.getPrefix(); // => Array of arrays of every well-known kind of prefixes grouped by alias
+```
+
 ### Quantity compatibility, kind and various queries
 
 ```javascript

spec/quantitiesSpec.js

@@ -1239,6 +1239,34 @@ describe("js-quantities", function() {
     });
   });
 
+  describe("Qty.getUnits", function() {
+    it("should return a dictionary of categories with array units grouped by alises", function() {
+      var units = Qty.getUnits(),
+        expectedKey = "length",
+        expectedValue = ["m","meter","meters","metre","metres"];
+
+      expect(units[expectedKey]).toContain(expectedValue);
+    });
+
+    it("should optionally restrict returned units to one category", function() {
+      var units = Qty.getUnits("area"),
+        unexpectedValue = ["stone","stones","st"],
+        expectedValue = ["acre","acres"];
+
+      expect(units).not.toContain(unexpectedValue);
+      expect(units).toContain(expectedValue);
+    });
+  });
+
+  describe("Qty.getPrefix", function() {
+    it("should return an array of array grouped by pefix", function() {
+      var prefixes = Qty.getPrefix(),
+          expectedValue = ["Ki","Kibi","kibi"];
+
+      expect(prefixes).toContain(expectedValue);
+    });
+  });
+
   describe("information", function() {
     describe("bits and bytes", function() {
       it("should have 'information' as kind", function() {

src/quantities.js

@@ -500,6 +500,77 @@ THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR IMPLI
     return (scalar + " " + units).trim();
   }
 
+/**
+   * Returns the object of available well-known units of per category 
+   * returning a list of list per category e.g.
+   *
+   * @param {EMPTY} no parameter
+   *
+   * @returns {Object[]} names of categoires as keys, with array of units grouped
+   * by aliases
+   *   mass:
+   *        [ [ 'kg', 'kilogram', 'kilograms' ], 
+   *        [ 'u', 'AMU', 'amu' ],
+   *        [ 'Da', 'Dalton', 'Daltons', 'dalton', 'daltons' ]]
+   *
+   * @param {string} kind - kind, string formated
+   *
+   * @returns {array} List of all units, group by alias
+   *
+   *  [ [ 'kg', 'kilogram', 'kilograms' ], 
+   *  ['u', 'AMU', 'amu' ],
+   *  [ 'Da', 'Dalton', 'Daltons', 'dalton', 'daltons']] 
+   */
+  Qty.getUnits = function(kind) {
+    var kinds = {},
+        k;
+    for (var unitId in UNITS) {
+        k = UNITS[unitId][2];
+        if (k.length === 0) {
+            continue;
+        }
+        if (kinds[k] === undefined) {
+            kinds[k] = [];
+        }
+        kinds[k].push(UNITS[unitId][0]);
+    }
+    if(kind) {
+        if(kinds[kind] === undefined) {
+            throw new QtyError(kind + ": Category not recognized.");
+        }
+        return kinds[kind];
+    }
+    return kinds;
+  };
+
+/**
+   * Returns the list of prefixes groups by prefix aliases e.g.
+   *   ["Ki","Kibi","kibi"]
+   *
+   * @returns {array[]} names of kinds as keys, with values of 
+   */
+  Qty.getPrefix = function() {
+    var prefixes = [];
+    for (var unitId in UNITS) {
+        if (UNITS[unitId][2] == "prefix"){
+            prefixes.push(UNITS[unitId][0]);
+        }
+    }
+    return prefixes;
+  };
+
+  /**
+   * Default formatter
+   *
+   * @param {number} scalar
+   * @param {string} units
+   *
+   * @returns {string} formatted result
+   */
+  function defaultFormatter(scalar, units) {
+    return (scalar + " " + units).trim();
+  }
+
   /**
    *
    * Configurable Qty default formatter