合并数组的相同的key值，并且计算相同key值的个数

[fxxqq]

需求：

合并数组的相同的key值，并且计算相同key值的个数

场景：

根据list数组的每一项的key值coupon_sn合并数组，并且计数

js代码

json数组：

let list = [{
    "id": 5899,
    "is_use": 0,
    "use_time": null,
    "expired_time": "2018-12-31 00:00:00",
    "coupon": {
        "coupon_sn": "1",
        "name": "满减",
        "type": 2,
        "count": 99993,
        "receive_count": 6,
        "is_fare": 0,
        "available_money": "2000.00",
        "reduce_money": "100.00",
        "discount": "1.000",
        "receive_start_time": "2018-07-27 00:00:00",
        "receive_end_time": "2020-12-31 00:00:00",
        "info": "",
        "created_at": "2018-07-27 21:22:51",
        "restriction_description": "仅限非板材使用"
    }
}, {
    "id": 5899,
    "is_use": 0,
    "use_time": null,
    "expired_time": "2018-12-31 00:00:00",
    "coupon": {
        "coupon_sn": "2",
        "name": "满减",
        "type": 2,
        "count": 99993,
        "receive_count": 6,
        "is_fare": 0,
        "available_money": "2000.00",
        "reduce_money": "100.00",
        "discount": "1.000",
        "receive_start_time": "2018-07-27 00:00:00",
        "receive_end_time": "2020-12-31 00:00:00",
        "info": "",
        "created_at": "2018-07-27 21:22:51",
        "restriction_description": "仅限非板材使用"
    }
}, {
    "id": 5899,
    "is_use": 0,
    "use_time": null,
    "expired_time": "2018-12-31 00:00:00",
    "coupon": {
        "coupon_sn": "2",
        "name": "满减",
        "type": 2,
        "count": 99993,
        "receive_count": 6,
        "is_fare": 0,
        "available_money": "2000.00",
        "reduce_money": "100.00",
        "discount": "1.000",
        "receive_start_time": "2018-07-27 00:00:00",
        "receive_end_time": "2020-12-31 00:00:00",
        "info": "",
        "created_at": "2018-07-27 21:22:51",
        "restriction_description": "仅限非板材使用"
    }
}]

js代码

 let hash = {
    coupon: {},
}, i = 0, res = [];
list.forEach(item = > {
    let coupon_sn = item.coupon.coupon_sn;
    if (hash[coupon_sn]) {
        if (!res[hash[coupon_sn] - 1].count) {
            res[hash[coupon_sn] - 1].count = 1
        }
        res[hash[coupon_sn] - 1].count += 1
    } else {
        hash[coupon_sn] = ++i && res.push({
            "count": 1,
            "id": item.id,
            "is_use": item.is_use,
            "use_time": item.use_time,
            "expired_time": item.expired_time,
            "coupon": item.coupon
        })
    }
});
console.log(res);