How to convert array of objects to object of array in javascript?

Question

I am trying to convert array of objects to object of array using javascript.

Here is the code

const data = [{
  yearMonthKey: "201907",
  dayKey: "15",
  startDate: "2019-07-15 00:00:00+0900",
  title: "testProgrma"
},
             {
  yearMonthKey: "201907",
  dayKey: "15",
  startDate: "2019-07-15 00:00:00+0900",
  title: "testProgrma"
},
            {
  yearMonthKey: "201907",
  dayKey: "16",
  startDate: "2019-07-15 00:00:00+0900",
  title: "testProgrma12313"
},
            {
  yearMonthKey: "201908",
  dayKey: "15",
  startDate: "2019-07-15 00:00:00+0900",
  title: "testProgrma"
}]

let programs = {};

I want to use programs object to make an object out of it like this below.

{
  201907: {
    15: [{
      yearMonthKey: "201907",
      dayKey: "15",
      startDate: "2019-07-15 00:00:00+0900",
      title: "testProgrma"
    },
        {
      yearMonthKey: "201907",
      dayKey: "15",
      startDate: "2019-07-15 00:00:00+0900",
      title: "testProgrma123132"
    }],
    16: [{
        yearMonthKey: "201907",
        dayKey: "16",
        startDate: "2019-07-15 00:00:00+0900",
        title: "testProgrma"
      }]
  },
    201908: {
      15: [{
        yearMonthKey: "201908",
        dayKey: "15",
        startDate: "2019-07-15 00:00:00+0900",
        title: "testProgrma"
      }]
    }
}

I try to solve it using map in array method.

data.map(item => {
  programs[item.yearMonthKey] : {
    programs[item.dayKey] : [{

    }]
  }
})

but it is bit challenging to sort objects as a value of same dayKey key inside of an array and put those inside of same yearMonthKey.

You can't use the function map when the desired result is a key-value object — Ele
– Ele, Commented Dec 13, 2019 at 12:31

adiga · Accepted Answer · 2019-12-13 12:39:40Z

5

You could reduce the array. Add each yearMonthKey to the accumulator. Based on the yearMonthKey add a nested dayKey key to the acc[yearMonthKey] object and default it to an array.

const data=[{yearMonthKey:"201907",dayKey:"15",startDate:"2019-07-15 00:00:00+0900",title:"testProgrma"},{yearMonthKey:"201907",dayKey:"15",startDate:"2019-07-15 00:00:00+0900",title:"testProgrma"},{yearMonthKey:"201907",dayKey:"16",startDate:"2019-07-15 00:00:00+0900",title:"testProgrma12313"},{yearMonthKey:"201908",dayKey:"15",startDate:"2019-07-15 00:00:00+0900",title:"testProgrma"}];

const output = data.reduce((acc, o) => {
  if (!acc[o.yearMonthKey]) 
    acc[o.yearMonthKey] = {};
    
  if (!acc[o.yearMonthKey][o.dayKey]) 
    acc[o.yearMonthKey][o.dayKey] = [];
    
  acc[o.yearMonthKey][o.dayKey].push(o);
  
  return acc;
}, {})

console.log(output)

edited Dec 13, 2019 at 12:39

answered Dec 13, 2019 at 12:33

adiga

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Comments

caramba · Accepted Answer · 2019-12-13 12:36:47Z

const data = [{
  yearMonthKey: "201907",
  dayKey: "15",
  startDate: "2019-07-15 00:00:00+0900",
  title: "testProgrma"
},
             {
  yearMonthKey: "201907",
  dayKey: "15",
  startDate: "2019-07-15 00:00:00+0900",
  title: "testProgrma"
},
            {
  yearMonthKey: "201907",
  dayKey: "16",
  startDate: "2019-07-15 00:00:00+0900",
  title: "testProgrma12313"
},
            {
  yearMonthKey: "201908",
  dayKey: "15",
  startDate: "2019-07-15 00:00:00+0900",
  title: "testProgrma"
}]

let programs = {};

data.forEach(function(element) {

    if (typeof programs[element.yearMonthKey] == "undefined") {
        programs[element.yearMonthKey] = {};
    }
    
    if(typeof programs[element.yearMonthKey][element.dayKey] == "undefined") {
        programs[element.yearMonthKey][element.dayKey] = [];
    }
    
    programs[element.yearMonthKey][element.dayKey].push(
        element
    );
});

console.log(programs);

Dmitry Reutov · Accepted Answer · 2019-12-13 12:46:18Z

Universal function for grouping with any keys

function group() {
   const args = Array.from(arguments)
   const data = args.shift()

   const result = {}
   data.forEach(elem => {
      let level = result
      args.forEach((groupProp, ind) => {
         const groupValue = elem[groupProp]
         if (groupValue in level) {
            level = level[groupValue]
         } else {
            level = level[groupValue] = ind === args.length - 1 ? [] : {}
         }
      })
      level.push(elem)
   })

   return result   
}

const data = [{
  yearMonthKey: "201907",
  dayKey: "15",
  startDate: "2019-07-15 00:00:00+0900",
  title: "testProgrma"
},
             {
  yearMonthKey: "201907",
  dayKey: "15",
  startDate: "2019-07-15 00:00:00+0900",
  title: "testProgrma"
},
            {
  yearMonthKey: "201907",
  dayKey: "16",
  startDate: "2019-07-15 00:00:00+0900",
  title: "testProgrma12313"
},
            {
  yearMonthKey: "201908",
  dayKey: "15",
  startDate: "2019-07-15 00:00:00+0900",
  title: "testProgrma"
}]

const result = group(data, 'yearMonthKey', 'dayKey')
console.log(result)

adiga · Accepted Answer · 2019-12-13 13:00:04Z

0

const data=[{yearMonthKey:"201907",dayKey:"15",startDate:"2019-07-15 00:00:00+0900",title:"testProgrma"},{yearMonthKey:"201907",dayKey:"15",startDate:"2019-07-15 00:00:00+0900",title:"testProgrma"},{yearMonthKey:"201907",dayKey:"16",startDate:"2019-07-15 00:00:00+0900",title:"testProgrma12313"},{yearMonthKey:"201908",dayKey:"15",startDate:"2019-07-15 00:00:00+0900",title:"testProgrma"}];

const dist_yearMonthKeys = [...new Set(data.map(d => d.yearMonthKey))];

let program = {};
for (let ymk of dist_yearMonthKeys) {
    const ymk_num = parseInt(ymk); // error-prone, be careful with your source data
    program[ymk_num] = {};
    const dist_dayKeys = [...new Set(data.filter(d => d.yearMonthKey === ymk).map(d => d.dayKey))];
    for (let dk of dist_dayKeys) {
        const dk_num = parseInt(dk); // error-prone
        program[ymk_num][dk_num] = data.filter(d => d.dayKey === dk && d.yearMonthKey === ymk);
    }
}

console.log(program);

This gives numeric keys, like you requested.

edited Dec 13, 2019 at 13:00

adiga

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answered Dec 13, 2019 at 12:37

igg

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1 Comment

adiga Over a year ago

There is no point in doing parseInt(ymk). Keys of an object are either a string or a Symbol. When you add program[ymk_num] it will be converted to a string.

maestro.inc · Accepted Answer · 2019-12-13 13:15:20Z

try destructuring the list and putting it back together in the format you want

const data = [{
  yearMonthKey: "201907",
  dayKey: "15",
  startDate: "2019-07-15 00:00:00+0900",
  title: "testProgrma"
},
             {
  yearMonthKey: "201907",
  dayKey: "15",
  startDate: "2019-07-15 00:00:00+0900",
  title: "testProgrma"
},
            {
  yearMonthKey: "201907",
  dayKey: "16",
  startDate: "2019-07-15 00:00:00+0900",
  title: "testProgrma12313"
},
            {
  yearMonthKey: "201908",
  dayKey: "15",
  startDate: "2019-07-15 00:00:00+0900",
  title: "testProgrma"
}]

const [1,2,3,4] = data

so now when you call variable 1 you would get

{
  yearMonthKey: "201907",
  dayKey: "15",
  startDate: "2019-07-15 00:00:00+0900",
  title: "testProgrma"
}

Now you can handle each object individually instead of in a list. As such you can basically do whatever you want with the objects

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