How to convert an object of just array values into an array of objects, each with transposed property values?

Question

What is the most efficient way to convert the data below in node.js? Any help would be much appreciated. Thanks!

I have some data that looks like this ->

const inputdata = {
  data1: [5.0, 10.0, 50.0, 100.0, 500.0],
  data2: [5.0, 10.0, 50.0, 100.0, 500.0],
  data3: [5.0, 10.0, 50.0, 100.0, 500.0],
};

and I need to convert it into this ->

[
  { data1: 5.0, data2: 5.0, data3: 5.0 },
  { data1: 10.0, data2: 10.0, data3: 10.0 },
  { data1: 50.0, data2: 50.0, data3: 50.0 },
  { data1: 100.0, data2: 100.0, data3: 100.0 },
  { data1: 500.0, data2: 500.0, data3: 500.0 },
]

Code attempt ->

const inputdata = {
  data1: [5.0, 10.0, 50.0, 100.0, 500.0],
  data2: [5.0, 10.0, 50.0, 100.0, 500.0],
  data3: [5.0, 10.0, 50.0, 100.0, 500.0],
};
const outputdata = [];

Object.keys(inputdata).forEach(key => {
  let value = inputdata[key];

  if (key === "data1"){
    for (let i = 0; i < value.length; i++) {
      outputdata.push({ data1: 0, data2: 0, data3: 0 });
    }
  }
}
Object.keys(inputdata).forEach(key => {
  let value = inputdata[key];

  if (key === "data1") {
    for (let i = 0; i < value.length; i++) {
      outputdata[i].data1 = value[i];
    }
  }
  if (key === "data2") {
    for (let i = 0; i < value.length; i++) {
      outputdata[i].data2 = value[i];
    }
  }
  if (key === "data3") {
    for (let i = 0; i < value.length; i++) {
      outputdata[i].data3 = value[i];
    }
  }
}
console.log(inputdata);
console.log(outputdata);

Nina Scholz · Accepted Answer · 2022-03-06 09:09:14Z

3

You could transpose the data and build new objects from data.

const
    data = { data1: [5, 10, 50, 100, 500], data2: [5, 10, 50, 100, 500], data3: [5, 10, 50, 100, 500] },
    result = Object
        .entries(data)
        .reduce((r, [k, a]) => a.map((v, i) => ({ ...r[i], [k]: v })), []);

console.log(result);

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

answered Mar 6, 2022 at 9:09

Nina Scholz

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Peter Seliger · Accepted Answer · 2022-03-06 11:15:27Z

1

Used techniques of the below provided step by step example code ...

// reducer function which transposes
// a table into a matrix and vice versa.
function transpose(result, row) {
  return row.reduce((matrix, value, idx) => {

    (matrix[idx] ??= []).push(value);
    return matrix;

  }, result);
}

const inputdata = {
  data1: [5.0, 10.0, 50.0, 100.0, 500.0],
  data2: [5.0, 10.0, 50.0, 100.0, 500.0],
  data3: [5.0, 10.0, 50.0, 100.0, 500.0]
};
console.log(
  Object

    // convert `inputdata` into a table
    // ... an array of row like arrays.
    .values(inputdata)
);
console.log(
  Object

    // - convert `inputdata` into a table
    //   ... an array of row like arrays.
    .values(inputdata)

    // - then transpose the table into a matrix.
    .reduce(transpose, [])
);
console.log(
  Object

    // - convert `inputdata` into a table
    //   ... an array of row like arrays.
    .values(inputdata)

    // - then transpose the table into a matrix.
    .reduce(transpose, [])

    // - then convert/map matrix 
    //   into an array of objects.
    .map(vector =>
      vector.reduce((object, value, idx) =>

        Object.assign(object, {
          [`data${ idx + 1 }`]: value,
        }), {}        
      )
    )
);

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

edited Mar 6, 2022 at 11:15

answered Mar 6, 2022 at 10:46

Peter Seliger

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1 Comment

Nina Scholz Over a year ago

try this with different key names of the object's arrays ...

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