# 渲染大量数据不卡

<!DOCTYPE html>
<html lang="en">
<head>
  <meta charset="UTF-8">
  <meta name="viewport" content="width=device-width, initial-scale=1.0">
  <meta http-equiv="X-UA-Compatible" content="ie=edge">
  <title>Document</title>
</head>
<body>
  <ul>控件</ul>
  <script>
    setTimeout(() => {
      // 插入十万条数据
      const total = 100000
      // 一次插入 20 条，如果觉得性能不好就减少
      const once = 20
      // 渲染数据总共需要几次
      const loopCount = total / once
      let countOfRender = 0
      let ul = document.querySelector("ul");
      function add() {
        // 优化性能，插入不会造成回流
        const fragment = document.createDocumentFragment();
        for (let i = 0; i < once; i++) {
          const li = document.createElement("li");
          li.innerText = Math.floor(Math.random() * total);
          fragment.appendChild(li);
        }
        ul.appendChild(fragment);
        countOfRender += 1;
        loop();
      }
      function loop() {
        if (countOfRender < loopCount) {
          window.requestAnimationFrame(add);
        }
      }
      loop();
    }, 0);
  </script>
</body>
</html>
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