javascript 常量
使用 const 我们仍然可以修改 javascript 对象的内容，但对该对象的引用将是不可变的。
const product = {name: "sugar", weight: "1 kg"};
product.name = "some new name";
console.log(product);
{
name: "some new name",
weight: "1 kg"
}
javascript 冻结
当我们不想修改对象的内容时，首选使用 freeze。
const product = {name: "sugar", weight: "1 kg"};
object.freeze(product);
product.name = "some new name";
console.log(product);
{
name: "Sugar",
weight: "1 kg"
}
