<link rel="stylesheet" href="style.css">

<script type="module" src="codeblock.js"></script>
<script type="module" src="scrollToTop.js"></script>

<scroll-to-top>
</scroll-to-top>

<a class="back" href="..">Module Index</a>

<h1 class="js module">debounce.js</h1>

<code-block>import debounce from 'debounce.js'</code-block>

<section>
	<h2>Description</h2>
	<p>
		Utility module for debouncing user-interactions (or any other events).
	</p>
	<p>
		Its main application are cases where expensive operations like updating or querying data are performed in response to some event like a user typing into a search box.
	</p>
	<dl>
		<code>
			<dt>debounce</dt>
			<dd>target &xrarr; wrapper</dd>
			<dd>target, timeout &xrarr; wrapper</dd>
		</code>
		<dd>
			A decorator function that takes a target function and returns a wrapper that will only call the target after a set timeout expires.
			Repeatedly calling the wrapper while the timeout is running will reset the timeout without calling the target function.
		</dd>
	</dl>


	<h2>Example</h2>

	<code-block>
		const update = value =&gt; expensive_operation(value)

		input.addEventListener("change", debounce(event =&gt; update(input.value)))
	</code-block>

	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 the following methods and properties:
		<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>
			<dt><code>running</code></dt>
			<dd><code>true</code> if there is a timeout currently running, <code>false</code> otherwise.</dd>
		</dl>
	</p>
</section>