# Const知识点

const实际上保证的，并不是变量的值不得改动，而是变量指向的那个内存地址所保存的数据不得改动。

如果真的想将对象冻结，应该使用Object.freeze方法。

```javascript
const foo = Object.freeze({});

// 常规模式时，下面一行不起作用；
// 严格模式时，该行会报错
foo.prop = 123;
```

除了将对象本身冻结，对象的属性也应该冻结。下面是一个将对象彻底冻结的函数。

```javascript
var constantize = (obj) => {
  Object.freeze(obj);
  Object.keys(obj).forEach( (key, i) => {
    if ( typeof obj[key] === 'object' ) {
      constantize( obj[key] );
    }
  });
};
```


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