Question 108780 in Javascript Question posted in
A very good W3school tutorial can be found here.

Javascript – Create object array base on different value

I have these data

[
    {
        "Month": 2,
        "SubjectID": 25,
        "TitleName": "TEST32",
        "Average": 85
    },
    {
        "Month": 4,
        "SubjectID": 1,
        "TitleName": "TEST",
        "Average": 63
    },
    {
        "Month": 4,
        "SubjectID": 25,
        "TitleName": "TEST32",
        "Average": 88
    }
]

i want to transform this into array object that will base on subject id and the month.
I don’t know if this is possible.

but i want to create a year array where the average will display in array index of created array base on month number.

Output like this

    {
        name: 'TEST',
        data: [0, 0, 0, 63, 0, 0, 0, 0, 0, 0, 0, 0]
    },
    {
        name: 'TEST32',
        data: [0, 85, 0, 88, 0, 0, 0, 0, 0, 0, 0, 0]
    }
Tags:

2

Answers


  1. 0 
    const data = [
  {
    "Month": 2,
    "SubjectID": 25,
    "TitleName": "TEST32",
    "Average": 85
  },
  {
    "Month": 4,
    "SubjectID": 1,
    "TitleName": "TEST",
    "Average": 63
  },
  {
    "Month": 4,
    "SubjectID": 25,
    "TitleName": "TEST32",
    "Average": 88
  }
];

const year = {};

// loop through each data item
data.forEach(item => {
  const { Month, SubjectID, TitleName, Average } = item;
  
  // if the SubjectID hasn't been seen yet, create an empty data array for it
  if (!year[SubjectID]) {
    year[SubjectID] = {
      name: TitleName,
      data: Array(12).fill(0)
    };
  }
  
  // update the data array for the current month with the average
  year[SubjectID].data[Month - 1] = Average;
});

// convert the year object into an array of objects
const yearArray = Object.values(year);

console.log(yearArray);
// output:
// [
//   {
//     name: 'TEST32',
//     data: [0, 85, 0, 88, 0, 0, 0, 0, 0, 0, 0, 0]
//   },
//   {
//     name: 'TEST',
//     data: [0, 0, 0, 63, 0, 0, 0, 0, 0, 0, 0, 0]
//   }
// ]

    First create an empty object called year, which will store the data for each SubjectID. We then loop through each item in the data array and check if the SubjectID has been seen before. If it hasn’t, we create a new object for it with an empty data array of length 12 (one for each month). If it has been seen before, we simply update the existing object’s data array for the current month with the Average value.

    Finally, we convert the year object into an array of objects using Object.values, and assign it to yearArray. This array contains one object for each unique SubjectID in the original data array, with the name property set to the TitleName and the data property set to an array of length 12 with the Average values in the appropriate positions.

    Login or Signup to reply.
  2. 0

    You could use Array#reduce with an object to store the 12 averages for each name.

    let arr=[{Month:2,SubjectID:25,TitleName:"TEST32",Average:85},{Month:4,SubjectID:1,TitleName:"TEST",Average:63},{Month:4,SubjectID:25,TitleName:"TEST32",Average:88}];
let res = Object.values(arr.reduce((acc, {Month, SubjectID, TitleName : name, Average}) => {
  (acc[name] ??= {name, data: Array(12).fill(0)}).data[Month - 1] = Average;
  return acc;
}, {}));
console.log(res);
    Login or Signup to reply.
Please signup or login to give your own answer.

Back To Top
Search