DebounceとThrottleの使い分け

Throttle(take first): 決められた時間単位内（delay）、最初のアクションしか実行しない

function throttle(fn, delay) {
  let timerId;
  let lastExecTime = 0;
  return () => {
    const context = this;
    const args = arguments;
    let elapsedTime = performance.now() - lastExecTime;
    const execute = () => {
      fn.apply(context, args);
      lastExecTime = performance.now();
    }
    if (!timerId) {
      execute();
    }
    if (timerId) {
      clearTimeout(timerId);
    }
    if (elapsedTime > delay) {
      execute();
    } else {
      timerId = setTimeout(execute, delay);
    }
  }
}

function debounce(fn, interval) {
  let timerId;
  return () => {
    clearTimeout(timerId);
    const context = this;
    const args = arguments;
    timerId = setTimeout(() => {
      fn.apply(context, args);
    }, interval);
  }
}