为什么?窗口.getComputedStyle()返回属性名为“backgroundColor”的对象,但使用属性名“backgroundColor”也可以吗?

console.log("background-color" in getComputedStyle(document.body));
console.log(
    Object.getOwnPropertyDescriptor(CSS2Properties.prototype, "background-color"));

for (let prop in document.body.style) {
  if (prop === "background-color") {
    console.log("found it");
  }
}

console.log(Object.getOwnPropertyDescriptor(document.body.style, "background-color"));

const magic = new Proxy({
  "background-color": "red",
}, {
  ownKeys(target) {
    return [];
  },
});

console.log(Object.keys(magic));
console.log(Object.getOwnPropertyDescriptor(magic, "background-color"));