Proxy and Reflect Article — Arrow Functions or `this` in Class constructor

まだ誰も着手していません。

**Source:** https://javascript.info/proxy
**Date Accessed:** 1 March 2022

A serious limitation in ES6 Proxy is the inability to proxy internal use of the `this` context inside a class. In the password example, if we use a class, then the differences in behaviour from using an arrow function vs a method is clear:

```ts

class User {

name = "John";
_password = "***";

checkPassword(value: string) {
return value === this._password;
}

checkPassword2 = (value: string) => {
return value === this._password;
}
};

const user = new Proxy(new User(), {

get(target: any, prop: string) {

if (prop.startsWith('_')) {
throw new Error("Access denied");
}
let value = target[prop];

// Commenting out the workaround
return value; // (typeof value === 'function') ? value.bind(target) : value; // (*)
},
});

console.log(user.checkPassword2('***')); // Arrow function works without the workaround because `this` is the internal context
console.log(user.checkPassword('***')); // Method fails with `Access denied` as expected

```

The point here is that if your class passes `this` somewhere in the constructor then that `this` cannot be proxied. This is a significant limitation of Proxy and should probably be mentioned in the article.

A good write up BTW.

Thanks

https://javascript.info/proxy の Proxy に関する記事から始め、報告されている class と arrow function の挙動と併せてパスワードの例を確認してください。内部での this の使用と Proxy を介したアクセスに関する制限を説明するように記事を更新してください。この区別と回避策の文脈が正確に文書化されていれば完了です。

索引モデルが issue の本文から書いたものです。