Transform JSON from an array of objects to objects of arrays

Question

Transform JSON from an array of objects to objects of arrays

I have a dataset of JSON entries:

[{"num": "1","name_A": "Alex" ,"name_B": "Bob"}, {"num": "2","name_A": "Anne" ,"name_B": "Barbra"}]

My goal is to effortlessly convert this collection of Objects into two separate objects - one labeled name_A, and the other as name_B. Each object should consist of the label and an array of corresponding num-name pairs:

[{title: "name_A", names:[{"1", "Alex}, {"2", "Anne"}]}, {title:"name_B", names: [{"1", "Bob"}, {"2", "Barbra"}]}]

Initially, I attempted to create the two objects by using array reduction twice, first for name_A and then for name_B before merging them together:

// obtain 'names' array
var name_A = objArray.reduce(function(memo, curr) {
    memo.push({curr.num, curr.name_A})
    return memo;
}, []);

However, my approach seems to be failing. Why is there no push method for memo when initializing reduce with an empty array?

Furthermore, am I steering in the right direction or is there a more efficient way to accomplish this task?

javascript arrays json functional-programming

Answer 1

Answer №1

Some minor corrections have been made to the expectations in the comments below.

var input = [{ "num": "1", "name_A": "Alex", "name_B": "Bob" }, { "num": "2", "name_A": "Anne", "name_B": "Barbra" }]

var output = input.reduce(function (a, b) {
    // Construct new objects and assign their properties
    var i = {};
    i[b.num] = b.name_A;
    var j = {};
    j[b.num] = b.name_B;

    // Add them to our collection elements
    a[0].names.push(i);
    a[1].names.push(j);

    return a;
   // Initialize our collection
}, [{ title: "name_A", names: [] }, { title: "name_B", names: [] }]);

// Print the output in a readable format
console.log(JSON.stringify(output, null, "     "))

var input = [{ "num": "1", "name_A": "Alex", "name_B": "Bob" }, { "num": "2", "name_A": "Anne", "name_B": "Barbra" }]

var output = input.reduce(function (a, b) {
  // Construct new objects and assign their properties
  var i = {};
  i[b.num] = b.name_A;
  var j = {};
  j[b.num] = b.name_B;

  // Add them to our collection elements
  a[0].names.push(i);
  a[1].names.push(j);

  return a;
  // Initializing our collection
}, [{ title: "name_A", names: [] }, { title: "name_B", names: [] }]);

so.log(output)

<pre id="output"></pre>
<script>
  var so = {
    log: function(o) {
      document.getElementById("output").innerHTML = JSON.stringify(o, null, "     ")
    }
  }
</script>

Answer 2

Some minor corrections have been made to the expectations in the comments below.

var input = [{ "num": "1", "name_A": "Alex", "name_B": "Bob" }, { "num": "2", "name_A": "Anne", "name_B": "Barbra" }]

var output = input.reduce(function (a, b) {
    // Construct new objects and assign their properties
    var i = {};
    i[b.num] = b.name_A;
    var j = {};
    j[b.num] = b.name_B;

    // Add them to our collection elements
    a[0].names.push(i);
    a[1].names.push(j);

    return a;
   // Initialize our collection
}, [{ title: "name_A", names: [] }, { title: "name_B", names: [] }]);

// Print the output in a readable format
console.log(JSON.stringify(output, null, "     "))

var input = [{ "num": "1", "name_A": "Alex", "name_B": "Bob" }, { "num": "2", "name_A": "Anne", "name_B": "Barbra" }]

var output = input.reduce(function (a, b) {
  // Construct new objects and assign their properties
  var i = {};
  i[b.num] = b.name_A;
  var j = {};
  j[b.num] = b.name_B;

  // Add them to our collection elements
  a[0].names.push(i);
  a[1].names.push(j);

  return a;
  // Initializing our collection
}, [{ title: "name_A", names: [] }, { title: "name_B", names: [] }]);

so.log(output)

<pre id="output"></pre>
<script>
  var so = {
    log: function(o) {
      document.getElementById("output").innerHTML = JSON.stringify(o, null, "     ")
    }
  }
</script>

Answer 3

Answer №2

Your code is encountering an issue because the object { curr.num, curr.name_A } lacks property names. To address this, I have included properties num and name in the revised code below.

var nameListA = [];
var nameListB = [];
objArray.forEach(function(curr) {
    nameListA.push({num: curr.num, name: curr.name_a});
    nameListB.push({num: curr.num, name: curr.name_B});
});
var modifiedResult = [ 
    { title: "name_A", names: nameListA },
    { title: "name_B", names: nameListB }
];

In addition, for creating an array from iterating over another array, it is recommended to utilize .map instead of .reduce.

Answer 4

Your code is encountering an issue because the object { curr.num, curr.name_A } lacks property names. To address this, I have included properties num and name in the revised code below.

var nameListA = [];
var nameListB = [];
objArray.forEach(function(curr) {
    nameListA.push({num: curr.num, name: curr.name_a});
    nameListB.push({num: curr.num, name: curr.name_B});
});
var modifiedResult = [ 
    { title: "name_A", names: nameListA },
    { title: "name_B", names: nameListB }
];

In addition, for creating an array from iterating over another array, it is recommended to utilize .map instead of .reduce.

Answer 5

Answer №3

Assuming that only the property num remains constant, all other properties are considered as data, such as name_A or name_B.

let items = [{ "num": "1", "name_A": "Alice", "name_B": "Ben" }, { "num": "2", "name_A": "Anna", "name_B": "Brian" }],
    finalResult = [];
items.forEach(function (element) {
    let number = element.num;
    Object.keys(element).forEach(function (key) {
        function findIndexAndAssignNames(arr, ind) {
            if (arr.title === key) {
                finalResult[ind].names[number] = element[key];
                return true;
            }
        }

        if (key !== 'num' && !finalResult.some(findIndexAndAssignNames)) {
            let newItem = {};
            newItem[number] = element[key];
            finalResult.push({ title: key, names: newItem });
        }
    });
});
document.write('<pre>' + JSON.stringify(finalResult, 0, 4) + '</pre>');

Answer 6

Assuming that only the property num remains constant, all other properties are considered as data, such as name_A or name_B.

let items = [{ "num": "1", "name_A": "Alice", "name_B": "Ben" }, { "num": "2", "name_A": "Anna", "name_B": "Brian" }],
    finalResult = [];
items.forEach(function (element) {
    let number = element.num;
    Object.keys(element).forEach(function (key) {
        function findIndexAndAssignNames(arr, ind) {
            if (arr.title === key) {
                finalResult[ind].names[number] = element[key];
                return true;
            }
        }

        if (key !== 'num' && !finalResult.some(findIndexAndAssignNames)) {
            let newItem = {};
            newItem[number] = element[key];
            finalResult.push({ title: key, names: newItem });
        }
    });
});
document.write('<pre>' + JSON.stringify(finalResult, 0, 4) + '</pre>');

Transform JSON from an array of objects to objects of arrays

Answer №1

Answer №2

Answer №3

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