声明变量const只能防止其值被新值替换。const对对象的内部状态没有任何限制。下例显示，const可以更改对象的属性值，甚至可以添加新的属性，因为分配给对象的对象person是修改的，但不能替换。
const person = {
name: "John"
};
console.log('The name of the person is', person.name);
person.name = "Steve";
console.log('The name of the person is', person.name);
person.surname = "Fox";
console.log('The name of the person is', person.name, 'and the surname is', person.surname);结果：
The name of the person is John The name of the person is Steve The name of the person is Steve and the surname is Fox
在此示例中，我们创建了名为的常量对象，person并重新分配了person.name属性并创建了新person.surname属性。