在不使用 .push() 的情况下减少对象数组

Question

我有这个对象数组：

[
    {
        user: 'User_1',
        date: 1603926000000,
        count: 3,
    },
    {
        user: 'User_2',
        date: 1603926000000,
        count: 10,
    },
    {
        user: 'User_2',
        date: 1604876400000,
        count: 1,
    },
]

我用这个函数减少它：

const reducedDataByDate = dataByDate.reduce((acc, d) => {
        const foundUser = acc.find((a) => a.user === d.user)
        const value = { date: formatDate(d.date), count: d.count }
        if (!foundUser) {
            acc.push({ user: d.user, data: [value] })
        } else {
            foundUser.data.push(value)
        }
        return acc
    }, [])

有了这个结果：

[
    {
        user: 'User_1',
        data: [
            {
                date: '2020-10-29',
                count: 10,
            },
            {
                date: '2020-11-09',
                count: 1,
            },
        ],
    },
    {
        user: 'User_2',
        data: [
            {
                date: '2020-10-29',
                count: 3,
            },
        ],
    },
]

理想情况下，我想摆脱将值推送到原始 acc 和 foundUser 数组，但不知道如何去做。非常感谢任何输入！

Answer 1

您可以使用Map 收集数据并从中获取所需的格式。

const 
    data = [{ user: 'User_1', date: 1603926000000, count: 3 }, { user: 'User_2', date: 1603926000000, count: 10 }, { user: 'User_2', date: 1604876400000, count: 1 }],
    result = Array.from(
        data.reduce(
            (m, { user, ...o }) => m.set(user, [...(m.get(user) || []), o]),
            new Map
        ),
        ([user, data]) => ({ user, data })
    );

console.log(result);

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