js实现图片局部放大

<div class="magnifier">
  <img src="path/to/image.jpg" alt="Image" id="magnifier-image">
  <div class="magnifier-lens" id="magnifier-lens"></div>
  <div class="magnifier-result" id="magnifier-result"></div>
</div>

.magnifier {
  position: relative;
  display: inline-block;
}

.magnifier-lens {
  position: absolute;
  border: 1px solid #000;
  width: 100px;
  height: 100px;
  background-color: rgba(255, 255, 255, 0.5);
  pointer-events: none;
  display: none;
}

.magnifier-result {
  position: absolute;
  top: 0;
  right: -100%;
  width: 300px;
  height: 300px;
  border: 1px solid #000;
  background-repeat: no-repeat;
  display: none;
}

document.addEventListener('DOMContentLoaded', function() {
  const image = document.getElementById('magnifier-image');
  const lens = document.getElementById('magnifier-lens');
  const result = document.getElementById('magnifier-result');

  const cx = result.offsetWidth / lens.offsetWidth;
  const cy = result.offsetHeight / lens.offsetHeight;

  image.addEventListener('mousemove', moveLens);
  lens.addEventListener('mousemove', moveLens);

  function moveLens(e) {
    e.preventDefault();
    const pos = getCursorPos(e);
    let x = pos.x - (lens.offsetWidth / 2);
    let y = pos.y - (lens.offsetHeight / 2);

    if (x > image.width - lens.offsetWidth) {
      x = image.width - lens.offsetWidth;
    }
    if (x < 0) {
      x = 0;
    }
    if (y > image.height - lens.offsetHeight) {
      y = image.height - lens.offsetHeight;
    }
    if (y < 0) {
      y = 0;
    }

    lens.style.left = x + 'px';
    lens.style.top = y + 'px';
    result.style.backgroundPosition = `-${x * cx}px -${y * cy}px`;
  }

  function getCursorPos(e) {
    let a = image.getBoundingClientRect();
    return {
      x: e.pageX - a.left - window.pageXOffset,
      y: e.pageY - a.top - window.pageYOffset
    };
  }

  image.addEventListener('mouseenter', () => {
    lens.style.display = 'block';
    result.style.display = 'block';
    result.style.backgroundImage = `url(${image.src})`;
    result.style.backgroundSize = `${image.width * cx}px ${image.height * cy}px`;
  });

  image.addEventListener('mouseleave', () => {
    lens.style.display = 'none';
    result.style.display = 'none';
  });
});