如何在 JSON 格式的对象数组中查找值的最大出现次数（最高计数）？答案

【问题标题】：How to find the max occurrence (highest count) of a value in an Array of Objects in JSON format?如何在 JSON 格式的对象数组中查找值的最大出现次数（最高计数）？
【发布时间】：2021-04-25 00:19:08
【问题描述】：

我有以下格式的数据：

 [
        {
            "product": "Term Insurance",
            "ViewTime": "Wed Jan 20 14:13:05 IST 2021",
            "userBought": true,
            "userLocation": {
                "loaded": true,
                "userAllowed": true,
                "coordinates": {
                    "lng": 70.8856,
                    "lat": 19.0748
                }
            },
            "category": "Health Insurance"
        },
        {
            "product": "Car Insurance",
            "ViewTime": "Wed Jan 20 15:40:31 IST 2021",
            "userBought": true,
            "userLocation": {
                "loaded": true,
                "userAllowed": true,
                "coordinates": {
                    "lng": 70.8856,
                    "lat": 19.0748
                }
            },
            "category": "Motor Insurance"
        },
        {
            "product": "Car Insurance",
            "ViewTime": "Wed Jan 20 15:42:52 IST 2021",
            "userBought": true,
            "userLocation": {
                "loaded": true,
                "userAllowed": true,
                "coordinates": {
                    "lng": 70.8856,
                    "lat": 19.0748
                }
            },
            "category": "Motor Insurance"
        }]

我想通过数组映射并使用 Javascript 从出现次数中计算 maxCategory 和 maxProduct。就像这里的 maxCategory 将是“汽车保险”，而 maxProduct 将是“汽车保险”。有什么干净、有效的方法吗？

【问题讨论】：

你试过了吗？什么不起作用？请添加您的代码。
请说明您所做的研究以及基于该研究所做的任何尝试。

标签： javascript arrays json reactjs loops

【解决方案1】：

你可以计算属性然后应用reduce方法，试试这个：

let cars = [
        {
            "product": "Term Insurance",
            "ViewTime": "Wed Jan 20 14:13:05 IST 2021",
            "userBought": true,
            "userLocation": {
                "loaded": true,
                "userAllowed": true,
                "coordinates": {
                    "lng": 70.8856,
                    "lat": 19.0748
                }
            },
            "category": "Health Insurance"
        },
        {
            "product": "Car Insurance",
            "ViewTime": "Wed Jan 20 15:40:31 IST 2021",
            "userBought": true,
            "userLocation": {
                "loaded": true,
                "userAllowed": true,
                "coordinates": {
                    "lng": 70.8856,
                    "lat": 19.0748
                }
            },
            "category": "Motor Insurance"
        },
        {
            "product": "Car Insurance",
            "ViewTime": "Wed Jan 20 15:42:52 IST 2021",
            "userBought": true,
            "userLocation": {
                "loaded": true,
                "userAllowed": true,
                "coordinates": {
                    "lng": 70.8856,
                    "lat": 19.0748
                }
            },
            "category": "Motor Insurance"
        }]

let counterCategories = {}
for (property of cars){
counterCategories[property.category] = 1 + (counterCategories[property.category] || 0)
}
console.log(counterCategories)


let entries = Object.entries(counterCategories);
let result = entries.reduce((acc, el) => acc[1] < el[1] ? el[0] : acc[0])
console.log('maxCategory: ' + result)

【讨论】：

【解决方案2】：

因为您正在寻找一种有效的方法来做到这一点。我使用了一个循环来找出结果。你可以检查一下。

const data = [
    {
        product: 'Term Insurance',
        ViewTime: 'Wed Jan 20 14:13:05 IST 2021',
        userBought: true,
        userLocation: {
            loaded: true,
            userAllowed: true,
            coordinates: {
                lng: 70.8856,
                lat: 19.0748,
            },
        },
        category: 'Health Insurance',
    },
    {
        product: 'Car Insurance',
        ViewTime: 'Wed Jan 20 15:40:31 IST 2021',
        userBought: true,
        userLocation: {
            loaded: true,
            userAllowed: true,
            coordinates: {
                lng: 70.8856,
                lat: 19.0748,
            },
        },
        category: 'Motor Insurance',
    },
    {
        product: 'Car Insurance',
        ViewTime: 'Wed Jan 20 15:42:52 IST 2021',
        userBought: true,
        userLocation: {
            loaded: true,
            userAllowed: true,
            coordinates: {
                lng: 70.8856,
                lat: 19.0748,
            },
        },
        category: 'Motor Insurance',
    },
];

let [maxProductCount, maxCategoryCount, maxProduct, maxCategory, tmpObj] = [0, 0, null, null, {}];

data.forEach(({ product, category }) => {
    tmpObj[product] = (tmpObj[product] || 0) + 1;
    tmpObj[category] = (tmpObj[category] || 0) + 1;
    if (tmpObj[product] > maxProductCount) {
        maxProductCount = tmpObj[product];
        maxProduct = product;
    }
    if (tmpObj[category] > maxCategoryCount) {
        maxCategoryCount = tmpObj[category];
        maxCategory = category;
    }
});

console.log({ maxProduct, maxCategory });

【讨论】：

【解决方案3】：

看看lodashcountBy方法：

let data = [...]
_.countBy(data, (item) => item.category);
// {"Health Insurance": 1, "Motor Insurance": 2}
_.countBy(data, (item) => item.product);
// {"Term Insurance": 1, "Car Insurance": 2}

【讨论】：