en.javascript.info/1-js/06-advanced-functions/09-call-apply-decorators/03-debounce/solution.md

function debounce(f, ms) {

  let isCooldown = false;

  return function() {
    if (isCooldown) return;

    f.apply(this, arguments);

    isCooldown = true;

    setTimeout(() => isCooldown = false, ms);
  };

}

The call to debounce returns a wrapper. There may be two states:

• isCooldown = false -- ready to run.
• isCooldown = true -- waiting for the timeout.

In the first call isCooldown is falsy, so the call proceeds, and the state changes to true.

While isCooldown is true, all other calls are ignored.

Then setTimeout reverts it to false after the given delay.