JavaScript：如何根据特定键/字段对json数组进行平均

Question

我想对特定键进行平均，例如

const users = [
  { name: 'Adam', age: 20, country: 'France', weight: 100 },
  { name: 'Adam', age: 28, country: 'Germany', weight: 100 },
  { name: 'Adam', age: 28, country: 'India', weight: 200 },
  { name: 'Adam', age: 40, country: 'France', weight: 200 },
  { name: 'Oliver', age: 28, country: 'France', weight: 200 }
];

键'age'和'weight'根据键'name'和'country'

取平均值

output = [
  { name: 'Adam', age: 30, country: 'France', weight: 150 },
  { name: 'Adam', age: 28, country: 'Germany', weight: 100 },
  { name: 'Adam', age: 28, country: 'India', weight: 200 },
  { name: 'Oliver', age: 28, country: 'France', weight: 200 }
];

删除未定义的键：

键 'age' 和 'weight' 根据键 'name'

取平均值

output = [
  { name: 'Adam', age: 29, weight: 150 },
  { name: 'Oliver', age: 28, weight: 200 }
];

Answer 1

您可以使用 filter、map 和 reduce 等函数来实现这些特定目标。

为确保键存在，您过滤掉缺少这些键的条目：

// Keep entries that have the age property
const cleanedUsers = users.filter(x => x.age)

为了得到用户的平均年龄，你可以将清理后的数组归约为一个数字，然后除以数组的长度。这可以在一行代码中完成。

const average = users.filter(x => x.age).reduce((acc,x) => acc + x.age, 0) / users.length

Answer 2

您可以按想要的键对其进行分组，并为每个组获取每个想要的属性的平均值。

function getAverages(array, groupKeys, averageKeys) {
    var groups = {},
        result = [];

    array.forEach(o => {
        var key = groupKeys.map(k => o[k]).join('|'),
            group = groups[key];

        if (!group) {
            groups[key] = { count: 0, payload: {} };
            group = groups[key];
            averageKeys.forEach(k => group[k] = 0);
            groupKeys.forEach(k => group.payload[k] = o[k]);
            result.push(group.payload);
        }
        groups[key].count++;
        averageKeys.forEach(k => group.payload[k] = (group[k] += o[k]) / group.count);
    })
    return result;
}

const users = [{ name: 'Adam', age: 20, country: 'France', weight: 100 }, { name: 'Adam', age: 28, country: 'Germany', weight: 100 }, { name: 'Adam', age: 28, country: 'India', weight: 200 }, { name: 'Adam', age: 40, country: 'France', weight: 200 }, { name: 'Oliver', age: 28, country: 'France', weight: 200 }];

console.log(getAverages(users, ['name', 'country'], ['age', 'weight']));
console.log(getAverages(users, ['name'], ['age', 'weight']));

.as-console-wrapper { max-height: 100% !important; top: 0; }

JavaScript：如何根据特定键/字段对json数组进行平均

JavaScript: How to average json array based on specific keys / fields

javascript

arrays

reduce

json

average