JavaScript で関数の完了を確実にする方法: コールバック、アロー関数、および Async/Await?

<code class="js">function firstFunction(_callback) {
  // Perform asynchronous work here...
  // Invoke the callback when finished
  _callback();
}

function secondFunction() {
  // Call first function with a callback
  firstFunction(function() {
    console.log('First function completed.');
  });
}</code>

<code class="js">firstFunction(() => console.log('First function completed.'));</code>

<code class="js">const secondFunction = async () => {
  const result = await firstFunction();
  // Continue execution after first function completes
};</code>