It helped me to start with the simple cases and then build up to the final solution.
For this problem, the simplest case is when <code>{leading: true, trailing: false}</code>, which is fairly straightforward to handle:
<pre class="shiki github-dark shaku"><code>function throttle(func, wait, option) { let waiting = false; return function wrapper(...args) { if(!waiting) { waiting = true; setTimeout(() =&gt; {waiting = false;}, wait); func.apply(this, args); } else { // do nothing } }}</code></pre>
From here, let us expand this solution to handle the case of <code>trailing = true</code>. This means that if the function is called once or more during a waiting period, we should execute the last such occurrence upon the waiting period ending. Let us update our solution to now:
<ul>
<li>keep track of the arguments to the last function call within a waiting period (<code>lastArgs</code>)</li>
<li>execute the function with <code>lastArgs</code> if it exists once the waiting period ends</li>
</ul>
<pre class="shiki github-dark shaku"><code>function throttle(func, wait, option = {leading: true, trailing: true}) { let waiting = false; let lastArgs = null; return function wrapper(...args) { if(!waiting) { waiting = true; // helper function to trigger a new waiting period const startWaitingPeriod = () =&gt; setTimeout(() =&gt; { // if at the end of the waiting period lastArgs exist, execute the function using it if(lastArgs) { func.apply(this, lastArgs); lastArgs = null; // start another waiting period startWaitingPeriod(); } else { waiting = false; } }, wait); func.apply(this, args); startWaitingPeriod(); } else { lastArgs = args; // store the arguments of the last function call within waiting period } }}</code></pre>
The last step is now to support the <code>leading=false</code> case. Here, instead of immediately invoking the function and then starting the waiting period, we do the opposite: start the waiting period, and then handle the function call in the same way that we do with any other function call during the waiting period.
<pre class="shiki github-dark shaku"><code>function throttle(func, wait, option = {leading: true, trailing: true}) { let waiting = false; let lastArgs = null; return function wrapper(...args) { if(!waiting) { waiting = true; const startWaitingPeriod = () =&gt; setTimeout(() =&gt; { if(option.trailing &amp;&amp; lastArgs) { func.apply(this, lastArgs); lastArgs = null; startWaitingPeriod(); } else { waiting = false; } }, wait); if(option.leading) { func.apply(this, args); } else { lastArgs = args; // if not leading, treat like another any other function call during the waiting period } startWaitingPeriod(); } else { lastArgs = args; } }}</code></pre>

Solution with explanation of thought process

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This is a follow up on 4. implement basic throttle(), please refer to it for detailed explanation. In this problem, you are asked to implement a enhan…