HTMLMapElement：areas 属性

<map id="image-map">
  <area shape="circle" coords="50,50,35" alt="左箭头" />
  <area shape="circle" coords="150,50,35" alt="右箭头" />
</map>
<img usemap="#image-map" src="left-right-arrow.png" alt="左右箭头图片" />
<output></output>

output {
  display: block;
}

const mapElement = document.getElementById("image-map");
const outputElement = document.querySelector("output");

for (const area of mapElement.areas) {
  area.addEventListener("click", (event) => {
    outputElement.textContent = `你点击了${area.alt}区域。\n\n`;
  });
}