Cannot redefine property: a at Function.defineProperty?

Question

这段代码会提示错误VM151:2 Uncaught TypeError: Cannot redefine property: a at Function.defineProperty,为什么不是输出a,b,c?

    let value = "a";
    Object.defineProperty(this, "a", {
      get() {
        let result = value;
        if (value === "a") {
          value = "b";
        } else if (value === "b") {
          value = "c";
        }
        return result;
      },
    });
    console.log(a,a,a);

Answer 1

这个报错是因为你执行了两次（或以上）这段代码。刷新后重新执行就好了。