从对象数组中的嵌套项计算数组中项的出现次数 javascript

Question

我有这个日期数组。

const dateArray = ["7/12/2021","7/13/2021","7/14/2021","7/15/2021"]

并且我正在尝试查看这些日期中的任何一个是否出现在我的其他对象数组中，这些日期将与对象中的某些内容匹配。

const data = [ 
      [ { id: 1, date: "7/13/2021" }, { id:2, date: "7/15/2021" } ],
      [ { id: 1, date: "7/14/2021" }, { id:2, date: "7/15/2021" } ],
]

所以如果日期不匹配，我想 return 0 作为那个日期。像这样

const result = [
     [0, 1, 0, 1],
     [0, 0, 1, 1]
]

我试过这样的东西......

var getResult = (dateArray, data) => {
    const result = []
    let index = 0;
    for (let i = 0; i < dateArray.length; i++) {
        for (let j = 0; j < data.length; j++) {
            let count = 0
            if (dateArray[i] === data[j][index].date) {
                count++
                index++
                if (index === data[i].length) {
                    return
                }
            }
            result.push(count)
        }
    }
    console.log(result)
}

但这当然行不通.... 感谢您的帮助！

Answer 1

你可以这样做

const dateArray = ["7/12/2021", "7/13/2021", "7/14/2021", "7/15/2021"];

const data = [
  [{
    id: 1,
    date: "7/13/2021"
  }, {
    id: 2,
    date: "7/15/2021"
  }],
  [{
    id: 1,
    date: "7/14/2021"
  }, {
    id: 2,
    date: "7/15/2021"
  }],
];

const result = data.map(item => {

  const resArr = (new Array(dateArray.length)).fill(0);
  item.forEach(entity => {
    const index = dateArray.findIndex(dateItem => dateItem == entity.date);
    if (index >= 0) {
      resArr[index]++;
    }
  });
  return resArr;
});

console.log(result);

Answer 2

const 
  dateArray = ["7/12/2021","7/13/2021","7/14/2021","7/15/2021"],
  data = [ 
    [ { id: 1, date: "7/13/2021" }, { id:2, date: "7/15/2021" } ],
    [ { id: 1, date: "7/14/2021" }, { id:2, date: "7/15/2021" } ],
  ];

// iterate over data
const result = data.map(arr => {
  // get occurences count of current array dates
  const occurences = arr.reduce((map, {date}) => 
    map.set(date, (map.get(data) || 0) + 1)
  , new Map);
  // return list of occurences for dateArray elements
  return dateArray.map(date => occurences.get(date) || 0);
}, []);

console.log(result);

从对象数组中的嵌套项计算数组中项的出现次数 javascript

count occurrences of items in an array from an nested items in an array of objects javascript

javascript

arrays

algorithm

object

find-occurrences