如何在JavaScript中为对象数组的每个作者单独计算阅读时长中位数

实现思路 #

你只需要先按作者分组收集所有对应readingTime数值，再对每个分组调用你已封装的中位数计算函数即可，完整可运行代码如下：

const bookDetails = [{"author":"john","readingTime":12123}, 
                     {"author":"romero","readingTime":908}, 
                     {"author":"romero","readingTime":1212}, 
                     {"author":"romero","readingTime":50}, 
                     {"author":"buck","readingTime":1902}, 
                     {"author":"buck","readingTime":12125}, 
                     {"author":"romero","readingTime":500},
                     {"author":"john","readingTime":10},
                     {"author":"romero","readingTime":230}, 
                     {"author":"romero","readingTime":189}, 
                     {"author":"legend","readingTime":12},
                     {"author":"john","readingTime":1890}]

// 你已实现的中位数计算函数
function medianof2Arr(arr1) {
    var concat = arr1;
    concat = concat.sort(function (a, b) { return a - b });
    var length = concat.length;

    if (length % 2 == 1) {
        return concat[(length / 2) - .5]
    } else {
        return (concat[length / 2] + concat[(length / 2) - 1]) / 2;
    }
}

// 按作者分组计算中位数的实现
function getAuthorReadingMedian(bookList) {
    // 1. 按作者分组收集readingTime
    const authorReadingMap = {}
    bookList.forEach(book => {
        if (!authorReadingMap[book.author]) {
            authorReadingMap[book.author] = []
        }
        authorReadingMap[book.author].push(book.readingTime)
    })

    // 2. 遍历分组计算每个作者的中位数
    const medianResult = {}
    Object.keys(authorReadingMap).forEach(author => {
        const medianVal = medianof2Arr(authorReadingMap[author])
        // 若需要和你给出的预期输出完全一致（对小数取整），可改为 medianResult[author] = Math.round(medianVal)
        medianResult[author] = medianVal
    })

    return medianResult
}

// 测试输出
console.log(getAuthorReadingMedian(bookDetails))
// 直接输出结果：{"john": 1890, "romero": 365, "buck": 7013.5, "legend": 12}
// 对buck的7013.5执行Math.round后即可得到你预期的7014

结果验证说明 #

• 作者john的readingTime排序后为[10, 1890, 12123]，长度为奇数，中位数就是中间值1890
• 作者romero的readingTime排序后为[50, 189, 230, 500, 908, 1212]，长度为偶数，中位数为(230+500)/2=365
• 作者buck的readingTime排序后为[1902, 12125]，中位数为(1902+12125)/2=7013.5，取整后为7014
• 作者legend的readingTime只有一个值12，中位数就是12

内容的提问来源于stack exchange，提问作者Siva Pradhan