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

Question

I have this array of dates.

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

and I am trying to see if any of these dates appear inside my other array of array of objects, those dates will match something inside the objects.

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" } ],
]

so if date doesn't match I want to return 0 for that date. something like this

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

I tried something like this.....

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)
}

but it doesn't work of course.... Thank you for your help!

Answer 1

 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);

Answer 2

You can do something like this

 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);