Question

我有一个数组：

[
    {
        "id": "#1",
        "quantity": 2
    },
    {
        "id": "#2",
        "quantity": 1
    },
    {
        "id": "#3",
        "quantity": 1
    },
    {
        "id": "#1",
        "quantity": 2
    },
    {
        "id": "#2",
        "quantity": 1
    },
    {
        "id": "#3",
        "quantity": 1
    }
]

我希望结果看起来像

[
    {
        "id": "#1",
        "quantity": 4
    },
    {
        "id": "#2",
        "quantity": 2
    },
    {
        "id": "#3",
        "quantity": 2
    }
]

基本上将具有相同ID的对象组合在一起，并将数量相加。我可以使用2 for循环来做到这一点。但是有没有更优化的方法来解决这个问题？

Answer 1

一个选项是首先将数组缩减为对象，如果键相同则添加数量，然后获取对象的值：

＆＃13;

var arr = [
    {
        "id": "#1",
        "quantity": 2
    },
    {
        "id": "#2",
        "quantity": 1
    },
    {
        "id": "#3",
        "quantity": 1
    },
    {
        "id": "#1",
        "quantity": 2
    },
    {
        "id": "#2",
        "quantity": 1
    },
    {
        "id": "#3",
        "quantity": 1
    }
]

console.log(
  Object.values(arr.reduce((obj, rec) => {
    if(obj[rec.id] === undefined) {
      obj[rec.id] = rec;
    } else {
      obj[rec.id].quantity += rec.quantity;
    }
    return obj;
  }, {}))
)

＆＃13;

Answer 2

这样的事情可以胜任：

function transform(a) {
    const seen = {};
    const ret = [];
    a.forEach(o => {
        const id = o.id;
        seen[id] = (seen[id] || 0) + o.quantity;
    });

    for (let key in seen) {
        ret.push({
            id: key,
            quantity: seen[key]
        });
    }
    return ret;
}
console.log(transform([{
    "id": "#1",
    "quantity": 2
}, {
    "id": "#2",
    "quantity": 1
}, {
    "id": "#3",
    "quantity": 1
}, {
    "id": "#1",
    "quantity": 2
}, {
    "id": "#2",
    "quantity": 1
}, {
    "id": "#3",
    "quantity": 1
}]));

合并数组中的常见对象并添加频率

2 个答案: