leetcode-problemset/leetcode/problem/timeout-cancellation.html

<p>Given a function <code>fn</code>, an array of&nbsp;arguments&nbsp;<code>args</code>, and a timeout&nbsp;<code>t</code>&nbsp;in milliseconds, return a cancel function <code>cancelFn</code>.</p>

<p>After a delay of <code>cancelTimeMs</code>, the returned cancel function <code>cancelFn</code> will be invoked.</p>

<pre>
setTimeout(cancelFn, cancelTimeMs)
</pre>

<p>Initially, the execution of the function <code>fn</code> should be delayed by <code>t</code> milliseconds.</p>

<p>If, before the delay of <code>t</code> milliseconds, the function <code>cancelFn</code> is invoked, it should cancel the delayed execution of <code>fn</code>. Otherwise, if <code>cancelFn</code> is not invoked within the specified delay <code>t</code>, <code>fn</code> should be executed with the provided <code>args</code> as arguments.</p>

<p>&nbsp;</p>
<p><strong class="example">Example 1:</strong></p>

<pre>
<strong>Input:</strong> fn = (x) =&gt; x * 5, args = [2], t = 20
<strong>Output:</strong> [{&quot;time&quot;: 20, &quot;returned&quot;: 10}]
<strong>Explanation:</strong> 
const cancelTimeMs = 50;
const result = [];

const fn = (x) =&gt; x * 5;

const start = performance.now();

const log = (...argsArr) =&gt; {
    const diff = Math.floor(performance.now() - start);
    result.push({&quot;time&quot;: diff, &quot;returned&quot;: fn(...argsArr)});
}
 &nbsp; &nbsp;&nbsp;
const cancel = cancellable(log, [2], 20);

const maxT = Math.max(t, 50);
&nbsp; &nbsp; &nbsp; &nbsp; &nbsp;&nbsp;
setTimeout(cancel, cancelTimeMs);

setTimeout(() =&gt; {
 &nbsp; &nbsp; console.log(result); // [{&quot;time&quot;:20,&quot;returned&quot;:10}]
}, maxT + 15);

The cancellation was scheduled to occur after a delay of cancelTimeMs (50ms), which happened after the execution of fn(2) at 20ms.
</pre>

<p><strong class="example">Example 2:</strong></p>

<pre>
<strong>Input:</strong> fn = (x) =&gt; x**2, args = [2], t = 100
<strong>Output:</strong> []
<strong>Explanation:</strong> 
const cancelTimeMs = 50;
The cancellation was scheduled to occur after a delay of cancelTimeMs (50ms), which happened before the execution of fn(2) at 100ms, resulting in fn(2) never being called.
</pre>

<p><strong class="example">Example 3:</strong></p>

<pre>
<strong>Input:</strong> fn = (x1, x2) =&gt; x1 * x2, args = [2,4], t = 30
<strong>Output:</strong> [{&quot;time&quot;: 30, &quot;returned&quot;: 8}]
<strong>Explanation: 
</strong>const cancelTimeMs = 100;
The cancellation was scheduled to occur after a delay of cancelTimeMs (100ms), which happened after the execution of fn(2,4) at 30ms.
</pre>

<p>&nbsp;</p>
<p><strong>Constraints:</strong></p>

<ul>
	<li><code>fn</code> is a function</li>
	<li><code>args</code> is a valid JSON array</li>
	<li><code>1 &lt;= args.length &lt;= 10</code></li>
	<li><code><font face="monospace">20 &lt;= t &lt;= 1000</font></code></li>
	<li><code><font face="monospace">10 &lt;= cancelTimeMs &lt;= 1000</font></code></li>
</ul>