从对象数组中的嵌套项目中计算数组中项目的出现次数javascript

如何解决从对象数组中的嵌套项目中计算数组中项目的出现次数javascript

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另一个对象数组中，这些日期将匹配对象中的某些内容。

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

因此，如果日期不匹配，我想为该日期返回 0。像这样

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

我尝试过这样的事情.....

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)
}

但它当然不起作用...... 感谢您的帮助！

解决方法

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" },];

// 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);

,

你可以这样做

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

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

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);