feat: allow custom dictionary patterns;

Closes #7

readme.md

@@ -34,20 +34,46 @@ stamp();
 
 ## API
 
-### tinydate(pattern)(date)
+### tinydate(pattern, dict?)(date?)
+Returns: `Function`
 
-#### pattern
+Returns a rendering function that will optionally accept a [`date`](#date) value as its only argument.
 
-Type: `string`
+#### pattern
+Type: `String`<br>
+Required: `true`
 
 The template pattern to be parsed.
 
-#### date
+#### dict
+Type: `Object`<br>
+Required: `false`
+
+A custom dictionary of template patterns. You may override [existing patterns](#patterns) or declare new ones.
+
+> **Important:** All dictionary items **must be a function** and must control its own formatting.<br>For example, when defining your own `{ss}` template, `tinydate` **will not** pad its value to two digits.
 
+```js
+const today = new Date('2019-07-04, 5:30:00 PM');
+
+// Example custom dictionary:
+//   - Adds {MMMM}
+//   - Overrides {DD}
+const stamp = tinydate('Today is: {MMMM} {DD}, {YYYY}', {
+	MMMM: d => d.toLocaleString('default', { month: 'long' }),
+	DD: d => d.getDate()
+});
+
+stamp(today);
+//=> 'Today is: July 4, 2019'
+```
+
+#### date
 Type: `Date`<br>
 Default: `new Date()`
 
-The date from which to retrieve values. Defaults to current datetime.
+The date from which to retrieve values. Defaults to current datetime if no value is provided.
+
 
 ## Patterns
 

src/index.js

@@ -1,6 +1,6 @@
 var RGX = /([^{]*?)\w(?=\})/g;
 
-var dict = {
+var MAP = {
 	YYYY: 'getFullYear',
 	YY: 'getYear',
 	MM: function (d) {
@@ -13,15 +13,16 @@ var dict = {
 	fff: 'getMilliseconds'
 };
 
-export default function (str) {
+export default function (str, custom) {
 	var parts=[], offset=0;
+
 	str.replace(RGX, function (key, _, idx) {
 		// save preceding string
 		parts.push(str.substring(offset, idx - 1));
 		offset = idx += key.length + 1;
 		// save function
-		parts.push(function (d) {
-			return ('00' + (typeof dict[key]==='string' ? d[dict[key]]() : dict[key](d))).slice(-key.length);
+		parts.push(custom && custom[key] || function (d) {
+			return ('00' + (typeof MAP[key] === 'string' ? d[MAP[key]]() : MAP[key](d))).slice(-key.length);
 		});
 	});
 

test/index.js

@@ -35,3 +35,29 @@ test('rendering', t => {
 
 	t.end();
 });
+
+test('customize', t => {
+	t.plan(5);
+
+	const tmpl = '{MMMM} {DD}, {YYYY}';
+
+	const stamp = fn(tmpl, {
+		// new key
+		MMMM: d => d.toLocaleString('default', { month: 'long' }),
+		// override key
+		DD: d => d.getDate()
+	});
+
+	t.is(typeof stamp, 'function', 'returns a function');
+	t.is(stamp(foo), 'May 1, 2017', 'returns formatted string w/ customized keys');
+
+	// instance w/o customized dictionary (DD should be 01 not 1)
+	t.is(render('{DD}'), '01', '~> does not leak {DD} customization into other instances');
+
+	try {
+		render(tmpl);
+	} catch (err) {
+		t.true(err instanceof TypeError, '~> throws TypeError w/ undefined {MMMM} format');
+		t.is(err.message, 'MAP[key] is not a function', '~> says {MMMM} is not a function');
+	}
+});