Web ページの再描画とリフローの数を減らす: Web ページのパフォーマンスを最適化する方法

<div id="myElement" class="red"></div>

<script>
  var element = document.getElementById('myElement');
  element.classList.toggle('red');
</script>

<ul id="myList">
  <li>Item 1</li>
  <li>Item 2</li>
  <li>Item 3</li>
</ul>

<script>
  var list = document.getElementById('myList');
  list.addEventListener('click', function(event) {
    if (event.target.tagName === 'LI') {
      console.log('You clicked on:', event.target.textContent);
    }
  });
</script>

var fragment = document.createDocumentFragment();

for (var i = 0; i < 1000; i++) {
  var element = document.createElement('div');
  element.textContent = 'Item ' + i;
  fragment.appendChild(element);
}

document.body.appendChild(fragment);

<div id="myElement"></div>

<style>
  #myElement {
    width: 100px;
    height: 100px;
    background-color: red;
    transition: width 1s;
  }

  #myElement:hover {
    width: 200px;
  }
</style>

function throttle(func, delay) {
  var timer = null;
  return function() {
    if (!timer) {
      timer = setTimeout(function() {
        func.apply(this, arguments);
        timer = null;
      }, delay);
    }
  };
}

function debounce(func, delay) {
  var timer = null;
  return function() {
    clearTimeout(timer);
    timer = setTimeout(function() {
      func.apply(this, arguments);
    }, delay);
  };
}

// 使用节流函数
window.addEventListener('scroll', throttle(function() {
  console.log('Scroll event');
}, 200));

// 使用防抖函数
window.addEventListener('resize', debounce(function() {
  console.log('Resize event');
}, 200));