为什么 X === (A || B || C) 不匹配任何内容？

Question

我有一个看起来像这样的数组：

const subscriptions = [
    {
        "price": "20",
        "product": "apple",
        "quantity": 1,
    },
    {
        "price": "10",
        "product": "orange",
        "quantity": 1,
    },
    {
        "price": "10",
        "product": "orange",
        "quantity": 1,
    },
    {
        "price": "10",
        "product": "orange",
        "quantity": 1,
    },
]

我想取出所有具有apple、banana或 的“乘积”的数组元素pear。

filter()所以我这样使用：

const currentPlans = subscriptions.filter(
  (subscription) =>
    subscription.product ===
    ('apple' || 'banana' || 'pear')
);

由于数组只有一个实例，apple因此应该currentPlans包含该实例。

但currentPlans返回一个空数组。

我究竟做错了什么？

Answer 1

以下行不会按您的预期工作。右侧首先计算一个值( apple)，然后检查是否相等。它从不检查banana或pear。

subscription.product === ("apple" || "banana" || "pear")

您应该使用另一个数组来保持匹配。尝试如下所示。

使用indexOf

subscription.product === ("apple" || "banana" || "pear")

使用包含

const subscriptions = [ { price: "20", product: "apple", quantity: 1, }, { price: "10", product: "orange", quantity: 1, }, { price: "10", product: "orange", quantity: 1, }, { price: "10", product: "orange", quantity: 1, }, ];

const matches = ["apple", "banana", "pear"];

const currentPlans = subscriptions.filter(
  (subscription) => matches.indexOf(subscription.product) >= 0
);

console.log(currentPlans);