reduce javascript array of objects

extraterrestrialmartian
April 3, 2023
198 views
3 votes
4 Answers

I have an Array of objects and I need to return this collection like Object and they key-names need to be indexes of length. I need to filter this object for it values.

Here is my code:

const data = [
  { index: 1, value: "111" },
  { index: 2, value: "121" },
  { index: 3, value: "111" },
  { index: 5, value: "111" },
  { index: 6, value: "121" },
  { index: 7, value: "121" },
];

const getGroupBy = (data) => {
  return data.reduce((acc, curr, currIndex, arr) => {
    const val = curr.value;
    const idx = curr.index;
    const fValues = arr.filter((el) => el.value === val).map(el => el.index);
    if (acc.hasOwnProperty(currIndex)) {
      acc[currIndex] = arr.filter((el) => el.value === val);
    } else {
      Object.assign(acc, { [0]: [idx] });
    }
    return acc;
  }, {});
};

console.log(getGroupBy(data));

My expected output is :

{
    0: [1,3,5],
    1: [2,6,7]
}

Answers

Is this not more useful, to key the arrays by their values instead of 0,1?

Anyway here is how to reduce and how to get either 0,1 keyed or keyed on value

const data = [
  { index: 1, value: "111" },
  { index: 2, value: "121" },
  { index: 3, value: "111" },
  { index: 5, value: "111" },
  { index: 6, value: "121" },
  { index: 7, value: "121" },
];

const indicii = data.reduce((acc,{index,value}) => {
  (acc[value] ??= []).push(index);
  return acc;
},{})
console.log({...Object.values(indicii)})
// or 
console.log(indicii);

Interesting method suggested here

const data = [
  { index: 1, value: "111" },
  { index: 2, value: "121" },
  { index: 3, value: "111" },
  { index: 5, value: "111" },
  { index: 6, value: "121" },
  { index: 7, value: "121" },
];

const indicii = data
  .reduce((acc,{index,value},i, arr) => {
    (acc[value] ??= []).push(index);
    return i < arr.length ? acc : {...Object.values(acc) }; // return the requested format at end
  },{});

console.log(indicii);

You could group and assign the values to an object.

const
    data = [{ index: 1, value: "111" }, { index: 2, value: "121" }, { index: 3, value: "111" }, { index: 5, value: "111" }, { index: 6, value: "121" }, { index: 7, value: "121" }],
    result = Object.assign(
        {},
        Object.values(data.reduce((r, { index, value }) => ((r[value] ??= []).push(index), r), {}))
    );

console.log(result);

.as-console-wrapper { max-height: 100% !important; top: 0; }

I think you have to go through the step

{value: [index]}
{0: value}

this step is help your code more cleaner

  const data = [
    { index: 1, value: '111' },
    { index: 2, value: '121' },
    { index: 3, value: '111' },
    { index: 5, value: '111' },
    { index: 6, value: '121' },
    { index: 7, value: '121' },
  ];

  const getGroupBy = (data) => {
    return data.reduce((acc, curr) => {
      if (acc[curr.value]) acc[curr.value].push(curr.index);
      else acc[curr.value] = [curr.index];
      return acc;
    }, {});
  };
  console.log(getGroupBy(data));
  console.log({ ...Object.values(getGroupBy(data)) });

The following code, I used reduce but last iteration, I changed the output to the desired one.

This is useful manytimes to get the desired output. when index is for last item, we are done with all the elements.

const data = [
  { index: 1, value: "111" },
  { index: 2, value: "121" },
  { index: 3, value: "111" },
  { index: 5, value: "111" },
  { index: 6, value: "121" },
  { index: 7, value: "121" },
];

const getGroupBy = (data) => {
  return data.reduce((acc, curr, index) => {
    const val = curr.value;
    const idx = curr.index;
    var key  = val;
     
    if (!acc[key]) {
      acc[key] = [];
    }
    acc[key].push(idx);

     if (index == data.length-1) {
      return Object.values(acc).reduce((a,c, i)=> { a[i]=c; return a;}, {});
    }
    return acc;
  }, {});
};


console.log(getGroupBy(data))

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