仿IOS桌面悬浮球（支持拖拽、自动吸附、自动改变透明度与点击、兼容PC端与移动端）

使用 pointerdown/pointermove/pointerup 实现仿IOS桌面悬浮球效果，支持拖拽、指定拖拽选对容器，指定拖拽安全区、自动吸附、自动改变透明度与点击，兼容PC端与移动端。

效果展示

在这里插入图片描述
https://code.juejin.cn/pen/7423757568268304421

代码实现

<!DOCTYPE html>
<html lang="en">

<head>
  <meta charset="UTF-8">
  <meta name="viewport" content="width=device-width, initial-scale=1.0">
  <title>Document</title>
  <style>
    * {
      margin: 0;
      padding: 0;
      box-sizing: border-box;
    }

    #app {
      width: 40px;
      height: 40px;
      background-color: rgba(0, 0, 0, 0.15);
      position: absolute;
      left: 50px;
      top: 50px;
      cursor: pointer;
      user-select: none;
      /** 处理移动端只能小范围拖动 */
      touch-action: none;
      border-radius: 50%;
      /** 处理移动端点击蓝色背景 */
      -webkit-tap-highlight-color: transparent;
    }

    #app::before,
    #app::after {
      content: '';
      display: block;
      width: 120%;
      height: 120%;
      border-radius: 50%;
      background-color: rgba(0, 0, 0, 0.15);
      position: absolute;
      top: 50%;
      left: 50%;
      transform: translate(-50%, -50%);
    }

    #app::after {
      width: 80%;
      height: 80%;
    }

    .parent {
      width: 50vw;
      height: 50vh;
      background-color: #f1f1f1;
    }
  </style>
</head>

<body>
  <div class="parent">
    <div id="app"></div>
  </div>

  <script>
    const initDrag = (app, options = {}) => {
      if (!app) return

      const {
        gaps = [10, 10], // 左右间距和上下间距（安全区）
        relative = 'window', // 相对容器 window | parent
        autoAdsorb = true, // 是否自动吸附
        autoAlpha = true, // 是否自动改变透明度
        onClick // 点击事件
      } = options

      let isPointerDown = false
      const parentRect = app.parentElement.getBoundingClientRect()
      const parentWidth = parentRect.width
      const parentHeight = parentRect.height
      let maxLeft = 0
      let maxTop = 0
      if (relative === 'parent') {
        maxLeft = ((parentWidth || window.innerWidth) - app.clientWidth) - gaps[0]
        maxTop = ((parentHeight || window.innerHeight) - app.clientHeight) - gaps[1]
      } else {
        maxLeft = window.innerWidth - app.clientWidth - gaps[0]
        maxTop = window.innerHeight - app.clientHeight - gaps[1]
      }
      let startLeft, startTop; // 记录开始位置

      app.addEventListener('pointerdown', function (e) {
        isPointerDown = true
        app.style.transition = 'none'
        app.style.opacity = 1

        startLeft = e.clientX;
        startTop = e.clientY;
      });

      app.addEventListener('pointermove', function (e) {
        app.setPointerCapture(e.pointerId)
        if (isPointerDown) {
          const left = app.getBoundingClientRect().left
          const top = app.getBoundingClientRect().top
          let newLeft = e.clientX - left
          let newTop = e.clientY - top

          let movedLeft = newLeft + left - app.clientWidth / 2
          let movedTop = newTop + top - app.clientHeight / 2

          // 限制上、左移出边界（默认边界为窗口宽高）
          movedLeft = Math.max(gaps[0], movedLeft)
          movedTop = Math.max(gaps[0], movedTop)

          // 限制下、右移出边界（默认边界为窗口宽高）
          movedLeft = Math.min(movedLeft, maxLeft)
          movedTop = Math.min(movedTop, maxTop)

          app.style.left = movedLeft + 'px'
          app.style.top = movedTop + 'px'
        }
      });

      // 自动降低透明度
      let autoAlphaTimer = null
      const handleAutoAlpha = () => {
        autoAlphaTimer && clearTimeout(autoAlphaTimer)
        autoAlphaTimer = setTimeout(() => {
          app.style.opacity = 0.7
        }, 1000)
      }

      // 自动吸附
      let autoAdsorbTimer = null
      const handleAutoAdsorb = () => {
        autoAdsorbTimer && clearTimeout(autoAdsorbTimer)
        autoAdsorbTimer = setTimeout(() => {
          const left = app.getBoundingClientRect().left
          const movedLeft = left > maxLeft / 2 ? maxLeft : gaps[0]
          app.style.transition = 'all 300ms ease-in-out'
          app.style.left = movedLeft + 'px'
          autoAlpha && handleAutoAlpha()
        }, 100)
      }

      app.addEventListener('pointerup', function (e) {
        isPointerDown = false

        // 判断是否为点击事件
        const endX = e.clientX;
        const endY = e.clientY;
        const distance = Math.sqrt((endX - startLeft) ** 2 + (endY - startTop) ** 2);

        // 如果移动距离小于 5 像素，则认为是点击
        if (distance < 5) {
          app.style.transition = 'none';
          app.style.opacity = 1;
          app.style.left = startLeft - app.clientWidth / 2 + 'px'
          app.style.top = startTop - app.clientHeight / 2 + 'px'

          onClick && onClick()
        } else {
          if (autoAdsorb) {
            handleAutoAdsorb()
          } else if (autoAlpha) {
            handleAutoAlpha()
          }
        }
      });
    }

    initDrag(document.getElementById('app'), {
      onClick: () => {
        alert('click')
      }
    })
  </script>
</body>

</html>