Circular const, let declaration for graph ...如何修复？

Question

好的，脑子冻结了……我需要帮助才能完成这项工作：

const a = {
  val: 'a',
  neighbor: d
}

const b = {
  val: 'b',
  neighbor: a
}

const c = {
  val: 'c',
  neighbor: b
}

const d = {
  val: 'd',
  neighbor: c
}

console.log('d: neighbor - > ', d.neighbor)
console.log('a: neighbor - > ', a.neighbor)

const a 必须指向 const d 但不幸的是 const d 是在之后定义的常量。在大多数情况下，我可以将 const a 移动到 const d 之后定义，但在这种情况下 const d 需要在 [=21= 之后定义]const c。我错过了什么......？谢谢

Answer 1

声明所有对象没有 "neighbor" 属性，然后在单独的赋值中添加。

const a = {
    val: 'a'
}

const b = {
    val: 'b'
}


const c = {
    val: 'c'
}

const d = {
    val: 'd'
}

a.neighbor = d;
b.neighbor = a;
c.neighbor = b;
d.neighbor = c;

Answer 2

您可以将 neighbor 属性定义为 getter。 getter 实际上是一个函数，它在您检索对象的值时执行，即此时所有引用的对象都已定义。这样您还可以保护 neighbor 属性免受意外更改。

const a = {
    val: 'a',
    get neighbor () {return d;}
};
const b = {
    val: 'b',
    get neighbor () {return a;}
};
const c = {
    val: 'c',
    get neighbor () {return b;}
};
const d = {
    val: 'd',
    get neighbor () {return c;}
};

console.log('d: neighbor - > ' , d.neighbor);
console.log('a: neighbor - > ' , a.neighbor);

Circular const, let declaration for graph ...如何修复？

Circular const, let declaration for graph ... how to fix?

javascript

scope

hoisting

ecmascript-6