Javascript parse json object and add 0's when fields are different

Question

I have a json object that has 3 fields: numbers, name, type, but type is not always present for every name. Here's my object:

myObj=
[{numbers: 10, name: object1, type: type1},
{numbers: 2, name: object1, type: type2}
{numbers: 15, name: object1, type: type3}
{numbers: 16, name: object1, type: type4}
{numbers: 12, name: object2, type: type2}
{numbers: 10, name: object2, type: type4}
{numbers: 1, name: object3, type: type3}
{numbers: 2, name: object4, type: type1}
{numbers: 4, name: object4, type: type2}
{numbers: 3, name: object4, type: type3}
{numbers: 1234, name: object4, type: type4}
]

As you can see no every object has all the types, and the resulting type arrays should have this structure:

finalNames = [object1, object2, object3, object4];
resultType1Array = [type1NumbersObject1, type1NumbersObject2, type1NumbersObject3, type1NumbersObject4];
resultType2Array = [type2NumbersObject1, type2NumbersObject2, type2NumbersObject3, type2NumbersObject4];
//and so on

The problem is that not every object contains all 4 types, and whenever I don't have a type I'd like to add a 0 in the position where it should belong to. So in my case it would be:

resultType1Array = [10, 0, 0, 2]
resultType2Array = [2, 12, 0, 4]
resultType3Array = [15, 0, 1, 3]
resultType4Array = [16, 10, 0, 1234]

but I can't insert 0's and I get arrays with wrong values. How can I achieve this solution? Here's my code:

myObj.forEach(v => names.push(v[Object.keys(v)[1]]));
myObj.forEach(v =>{
if(v.Type === "type1"){
    resultType1Array.push(v[Object.keys(v)[0]]);
}
if(v.Type === "type2"){
    resultType2Array.push(v[Object.keys(v)[0]]);
}
if(v.Type === "type3"){
    resultType3Array.push(v[Object.keys(v)[0]]);
}
if(v.Type === "type4"){
    resultType4Array.push(v[Object.keys(v)[0]]);
}


totalNames = [...new Set(names)];

})

The result I get can have a variable number of elements in the array depending on the existence or not of a type in the object. This is my result:

resultType1Array = [10, 2]
resultType2Array = [2, 12, 4]
resultType3Array = [15, 1, 3]
resultType4Array = [16, 10, 1234]

How can I place a 0 in the correct position of the resultArray if the name doesn't have that specific type? Thank you

Lakshya · Accepted Answer · 2021-05-17 18:17:33Z

1

You just need to create an array of length 4 (or n where n is the largest number of object) and initialise it with zeros. Then you can insert the value right at that index and leave out the rest.

The following code works for 4 objects (as array is initialized with 4) but you can easily extend it for n objects by finding or passing the argument to the function of largest object number possible.

var myObj = [{
    numbers: 10,
    name: 'object1',
    type: 'type1'
  },
  {
    numbers: 2,
    name: 'object1',
    type: 'type2'
  },
  {
    numbers: 15,
    name: 'object1',
    type: 'type3'
  },
  {
    numbers: 16,
    name: 'object1',
    type: 'type4'
  },
  {
    numbers: 12,
    name: 'object2',
    type: 'type2'
  },
  {
    numbers: 10,
    name: 'object2',
    type: 'type4'
  },
  {
    numbers: 1,
    name: 'object3',
    type: 'type3'
  },
  {
    numbers: 2,
    name: 'object4',
    type: 'type1'
  },
  {
    numbers: 4,
    name: 'object4',
    type: 'type2'
  },
  {
    numbers: 3,
    name: 'object4',
    type: 'type3'
  },
  {
    numbers: 1234,
    name: 'object4',
    type: 'type4'
  }
]

function createArray(arr, largestObjectNumber = 4) {

  var res = [];
  var map = {};

  arr.forEach(item => {
    if (map[item.type]) {
      map[item.type] = [...map[item.type], item];
    } else {
      map[item.type] = [item];
    }
  });

  for (let i in map) {
    var ans = new Array(largestObjectNumber).fill(0);

    map[i].forEach(item => {
      ans[parseInt(item.name.match(/\d+/), 10) - 1] = item.numbers;
    });

    res.push(ans);
  }

  return res;
}

console.log(createArray(myObj));

answered May 17, 2021 at 18:17

Lakshya

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8 Comments

thranduil90 Over a year ago

Thanks! But it is returning arrays full of 0's. Do you know why?

Lakshya Over a year ago

It may be because I had assumed the name a string type (used "object1" instead of object1 just like the type of "type" field is supposed to be string) in the input. You may run the code snippet here and check the code in the answer. If the type of name is not string, code will change.

thranduil90 Over a year ago

name is a string, type is a string and numbers is an int. It returns all 0's anyway. The list of arrays I'm returning are similar to this [0,0,0,0, NaN: 3]

thranduil90 Over a year ago

what does that mean?

Lakshya Over a year ago

Are you calling the function correctly? Check the code in the answer. And here's a link of the screenshot i.ibb.co/vm7xHjG/stack.png with the output that I am getting.

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