feat(formats): allow fractions in percentage formatting

README.md

@@ -179,6 +179,9 @@ The following standard format strings can be applied to a template expression of
 console.log(i18n`Hello ${name}, the percentage is ${0.01}:p.`)
 // Hello Steffen, the percentage is 1%.
 
+console.log(i18n`Hello ${name}, the percentage is ${0.005}:p(1).`)
+// Hello Steffen, the percentage is 0.5%.
+
 i18nConfig({
     locales: 'de-DE'
 })

__tests__/__snapshots__/es2015-i18n-tag.test.js.snap

@@ -22,6 +22,8 @@ exports[`es2015-i18n-tag should format fractionals 1`] = `"Hello Steffen, the nu
 
 exports[`es2015-i18n-tag should format percentage 1`] = `"Hello Steffen, the percentage is 10%."`;
 
+exports[`es2015-i18n-tag should format percentage with fractions 1`] = `"Hello Steffen, the percentage is 0.1%."`;
+
 exports[`es2015-i18n-tag should ignore missing standard formatters 1`] = `"The date is 20.12.2012, 18:00:00 test123."`;
 
 exports[`es2015-i18n-tag should ignore unknown custom number formatters 1`] = `"Hello Steffen, the number is 0.137."`;

__tests__/es2015-i18n-tag.test.js

@@ -221,6 +221,18 @@ describe('es2015-i18n-tag', () => {
         expect(actual).toMatchSnapshot()
     })
 
+    it('should format percentage with fractions', () => {
+        const name = 'Steffen'
+        const percentage = 0.001
+
+        i18nConfig({
+            locales: 'en-US'
+        })
+
+        const actual = i18n`Hello ${name}, the percentage is ${percentage}:p(1).`
+        expect(actual).toMatchSnapshot()
+    })
+
     it('should format currency', () => {
         const name = 'Steffen'
         const amount = 0.1

lib/index.js

@@ -221,11 +221,14 @@ class Tag {
                     Object.assign({}, config.number, { style: numberStyleCurrency })
                 )
             },
-            p /*percent*/: (config, v) => {
+            p /*percent*/: (config, v, minimumFractionDigits) => {
                 if((typeof v) !== 'number') {
                     throw Error(`value is not a number. type: ${typeof v}`)
                 }
-                return v.toLocaleString(config.locales, Object.assign({}, config.number, { style: numberStylePercent }))
+                return v.toLocaleString(config.locales, (minimumFractionDigits) ?
+                    Object.assign({}, config.number, { style: numberStylePercent, minimumFractionDigits }) :
+                    Object.assign({}, config.number, { style: numberStylePercent })
+                )
             }
         }
         this.i18n = this.i18n.bind(this)