如何根据背景图片的宽度设置div的高度？

.div-class {
  background-image: url("背景图片地址");
  background-size: cover;
  padding-top: 56.25%;
}

.div-class {
  background-image: url("背景图片地址");
  background-size: cover;
  position: relative;
}

.div-class::before {
  content: "";
  display: block;
  padding-top: 56.25%;
}

<div id="div-id" style="background-image: url('背景图片地址'); background-size: cover;"></div>

<script>
  window.onload = function() {
    var div = document.getElementById("div-id");
    var backgroundImage = new Image();
    backgroundImage.src = div.style.backgroundImage.slice(4, -1).replace(/"/g, "");
    backgroundImage.onload = function() {
      var width = backgroundImage.width;
      var height = backgroundImage.height;
      var aspectRatio = height / width;
      var divWidth = div.offsetWidth;
      var divHeight = divWidth * aspectRatio;
      div.style.height = divHeight + "px";
    };
  };
</script>