JavaScript: setTimeout does NOT require a clearTimeout unless you want to cancel it before it fires (once)

set-clearTimeout.html

<!-- Ref: https://developer.mozilla.org/en-US/docs/Web/API/setTimeout#examples -->
<button onclick="delayedMessage();">Show a message after two seconds</button>
<button onclick="clearMessage();">Cancel message before it happens</button>

<div id="output"></div>
<script>
  let timeoutID;

  function setOutput(outputContent) {
    console.log("setOutput() called");
    document.querySelector("#output").textContent += outputContent;
  }

  function delayedMessage() {
    timeoutID = setTimeout(setOutput, 2 * 1000, "That was really slow!");
  }

  function clearMessage() {
    clearTimeout(timeoutID);
  }
</script>