Question

我尝试使用Array.reduce的组合，同时遍历数据以提供将数组中的值加在一起的结果，但前提是它们必须具有另一个匹配属性，并且我的数组示例是：

{"2018":[{"leaveYear":2018,"dayValue":60},{"leaveYear":2018,"dayValue":60}], "2019":[{"leaveYear":2019,"dayValue":60}]}

使用上面的示例，我想做的就是获取每个dayValue的总和，但是仅当它们的leaveYear匹配时才可以。所以我的结果是：
2018：120
2019：60

然后，将这些数据存储在我的数据库中，以leaveYear作为键，并将简化的dayValue作为值

我的进度
我首先创建新的数组，将这些数组对象按leaveYear进行分组，因为它们可以是任何年份，也可以使用以下任意顺序：

function getSum(total, num) {
    return total + num;
    }
//used to total my values

function groupBy(array, property) {
        var hash = {};
        for (var i = 0; i < array.length; i++) {
            if (!hash[array[i][property]]) hash[array[i][property]] = [];
            hash[array[i][property]].push(array[i]);
        }
        return hash;
    }

哪个会生成对象数组，每个对象的年份都匹配。然后，通过再次遍历，我开始减少：

var grouped = groupBy(multiSelectSaveArr,'leaveYear')
var multiDeductTotal = []
// my array of arrays by leaveYear

            for(var i in grouped) {
                var splitGroup = grouped[i]
                console.log("SPLITGROUP:" + JSON.stringify(splitGroup))

//my log shows the result of

//SPLITGROUP:[{"leaveYear":2018,"dayValue":60},{"leaveYear":2018,"dayValue":60}]
//SPLITGROUP:[{"leaveYear":2019,"dayValue":60}]
//I then loop through splitGroup to reduce for my desired result by doing the following:

                for(var ix in splitGroup) {
                    multiDeductTotal.push([splitGroup[ix].dayValue])
                }

                var deductReduce = 0 + multiDeductTotal.reduce(getSum)
//signal to database storing data
                calendarPage.amendTakenAllowance(deductReduce, year)
            }

我的问题是
这样做时，有时效果很好，但是当添加更多数组对象或几个leaveYears时，循环有时似乎跳过或错过了数字，仅减少了给定{的值，或者没有{1}}

我如何遍历数组的每个leaveYear，以减少信号并将其发送到数据库，然后再移至下一组值？

感谢您的帮助！

Answer 1

您的输入是一个对象，其值是数组，您需要为原始对象中的每个键值对创建一个新对象。为此，您可以.map将每个内部数组都放入一个条目中，并用dayValue将数组中每个项目的.reduce s相加，然后再转换为一个对象Object.fromEntries：

const input = {
  "2018": [{
    "leaveYear": 2018,
    "dayValue": 60
  }, {
    "leaveYear": 2018,
    "dayValue": 60
  }],
  "2019": [{
    "leaveYear": 2019,
    "dayValue": 60
  }]
};
const sumDays = yearArr => yearArr.reduce((a, b) => a + b.dayValue, 0);
const output = Object.fromEntries(
  Object.values(input).map(yearArr => ([yearArr[0].leaveYear, sumDays(yearArr)]))
);
console.log(output);

如果您不能使用fromEntries，则可以reduce进入输出对象：

const input = {
  "2018": [{
    "leaveYear": 2018,
    "dayValue": 60
  }, {
    "leaveYear": 2018,
    "dayValue": 60
  }],
  "2019": [{
    "leaveYear": 2019,
    "dayValue": 60
  }]
};
const sumDays = yearArr => yearArr.reduce((a, b) => a + b.dayValue, 0);
const output = Object.values(input).reduce((a, yearArr) => {
  a[yearArr[0].leaveYear] = sumDays(yearArr);
  return a;
}, {});
console.log(output);

在for-in循环中的特定数组属性上使用JS Array.Reduce

1 个答案: