Add support for number formatting

Author: codeandcats

Readme.md

@@ -45,7 +45,7 @@ This module uses a pre-defined list of rules, applied in order, to singularize o
 
 * `word: string` The word to pluralize
 * `count: number` How many of the word exist
-* `inclusive: boolean` Whether to prefix with the number (e.g. 3 ducks)
+* `inclusive: boolean | Intl.NumberFormat | (amount: number) => string` Whether to prefix with the number (e.g. 3 ducks)
 
 Examples:
 
@@ -58,6 +58,12 @@ pluralize('test', 1, true) //=> "1 test"
 pluralize('test', 5, true) //=> "5 tests"
 pluralize('蘋果', 2, true) //=> "2 蘋果"
 
+// Example of formatting numbers
+pluralize('test', 1.57, amount => amount.toFixed(1)) //=> "1.6 tests"
+
+const formatter = new Intl.NumberFormat(undefined, { useGrouping: true, maximumFractionDigits: 1 })
+pluralize('test', 1234567.89, formatter) //=> "1,234,567.9 tests"
+
 // Example of new plural rule:
 pluralize.plural('regex') //=> "regexes"
 pluralize.addPluralRule(/gex$/i, 'gexii')

pluralize.js

@@ -164,19 +164,41 @@
     };
   }
 
+  /**
+   * Returns the formatted number prefix (or an empty string)
+   *
+   * @param {number} amount The number to format
+   * @param {boolean | Intl.NumberFormat | (amount: number) => string} inclusive Whether to prefix with the number (e.g. 3 ducks). Can also be a function that formats the number, or an Intl.NumberFormat instance.
+   */
+  function getNumberPrefix (amount, inclusive) {
+    if (!inclusive) return '';
+
+    if (typeof inclusive === 'function') {
+      const formatted = inclusive(amount);
+      return formatted !== '' ? formatted + ' ' : '';
+    }
+
+    if (inclusive instanceof Intl.NumberFormat) {
+      const formatted = inclusive.format(amount);
+      return formatted !== '' ? formatted + ' ' : '';
+    }
+
+    return amount + ' ';
+  }
+
   /**
    * Pluralize or singularize a word based on the passed in count.
    *
    * @param  {string}  word      The word to pluralize
    * @param  {number}  count     How many of the word exist
-   * @param  {boolean} inclusive Whether to prefix with the number (e.g. 3 ducks)
+   * @param  {boolean | Intl.NumberFormat | (amount: number) => string} inclusive Whether to prefix with the number (e.g. 3 ducks). Can also be a function that formats the number, or an Intl.NumberFormat instance.
    * @return {string}
    */
   function pluralize (word, count, inclusive) {
     var pluralized = count === 1
       ? pluralize.singular(word) : pluralize.plural(word);
 
-    return (inclusive ? count + ' ' : '') + pluralized;
+    return getNumberPrefix(count, inclusive) + pluralized;
   }
 
   /**

test.js

@@ -782,6 +782,33 @@ describe('pluralize', function () {
     it('singular words', function () {
       expect(pluralize('test', 1, true)).to.equal('1 test');
     });
+
+    it('formats using Intl.NumberFormat', function () {
+      expect(pluralize('test', 1234567.89, new Intl.NumberFormat('en-US', { useGrouping: true, maximumFractionDigits: 1 }))).to.equal('1,234,567.9 tests');
+    });
+
+    it('formats using function', function () {
+      expect(pluralize('test', 1234567.89, (amount) => amount.toFixed(1))).to.equal('1234567.9 tests');
+    });
+
+    it('formats using function which returns number as is', function () {
+      expect(pluralize('test', 1234567.89, (amount) => amount)).to.equal('1234567.89 tests');
+    });
+
+    it('excludes extra space when format function returns empty string', function () {
+      expect(pluralize('test', 1234567.89, () => '')).to.equal('tests');
+    });
+
+    it('excludes extra space when Intl.NumberFormat returns empty string', function () {
+      // Not sure if it's possible for Intl.NumberFormat to return an empty string
+      // so just patching it to force one just in case, so we get the test coverage
+      const formatter = new Intl.NumberFormat();
+      Object.defineProperty(formatter, 'format', {
+        value: () => ''
+      });
+
+      expect(pluralize('test', 1234567.89, formatter)).to.equal('tests');
+    });
   });
 
   describe('adding new rules', function () {