Add cancellability to debounce wrapper

debounce.js

@@ -1,10 +1,19 @@
 export default (action, delay=1e3) => {
 	let timeout
-	return (...args) => {
+	const func = (...args) => {
 		if (timeout) clearTimeout(timeout)
 		timeout = setTimeout(() => {
 			timeout = undefined
 			action(...args)
 		}, delay)
 	}
+	func.cancel = () => {
+		if (timeout) clearTimeout(timeout)
+		timeout = undefined
+	}
+	func.now = (...args) => {
+		func.cancel()
+		return action(...args)
+	}
+	return func
 }

page/debounce.html

@@ -38,4 +38,15 @@
 
 	This code will debounce the update event handler of an input element, calling the <code>update</code>
 	function only after no changes have been made for at least one second.
+
+	<h2>Methods</h2>
+	<p>
+		The returned wrapper function has two methods:
+		<dl>
+			<dt><code>cancel()</code></dt>
+			<dd>Cancels the running timeout without calling the target function.</dd>
+			<dt><code>now(...)</code></dt>
+			<dd>Cancels the running timeout and calls the target function immediately.</dd>
+		</dl>
+	</p>
 </section>