convert an array of objects into a specific format?

Question

I have the below set of data that is in the format of objects within an array.


  const columns = [
    {
      "usage": 395226,
      "population": 1925117,
      "value": 21,
      "abv": "MN"
    },
    {
      "usage": 893129,
      "population": 4327541,
      "value": 21,
      "abv": "IL"
    }
  ]

I require the above set of data to be converted into below shown format. I have been stuck here for a while. I tried writing a function for converting this into the desired data format, but it didn't work.


let columns = [ 
                 ["abv", "population"], 
                 ["MN", 1925117], 
                 ["IL", 4327541] 
              ]

It would be a great help if anyone could help me solve this. Thanks in advance :)

Possible duplicate of Typescript: Is there a simple way to convert an array of objects of one type to another — Harun Yilmaz
– Harun Yilmaz, Commented Oct 7, 2019 at 11:09
You should at least provide some code to show what you tried and where you got stuck. — sander
– sander, Commented Oct 7, 2019 at 11:11
@HarunYilmaz This is not a duplicate of that question, as this one is pure javascript and not TypeScript. — Tony Abrams
– Tony Abrams, Commented Oct 7, 2019 at 11:12
Please explain if there is any pattern in the new format that you require. — zetawars
– zetawars, Commented Oct 7, 2019 at 11:13
@TonyAbrams Array.map() is not a TypeScript-specific feature. See: developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/… — Harun Yilmaz
– Harun Yilmaz, Commented Oct 7, 2019 at 11:14

Ivor · Accepted Answer · 2019-10-07 11:26:27Z

0

I would do it with a reducer:

 const cols = [
    {
      "usage": 395226,
      "population": 1925117,
      "value": 21,
      "abv": "MN"
    },
    {
      "usage": 893129,
      "population": 4327541,
      "value": 21,
      "abv": "IL"
    }
  ]

cols.reduce(function(acc, current) {
  acc.push([current.abv, current.population])
  return acc;
}, ["abv", "population"]);

Or if you don't like using push:

cols.reduce(function(acc, current) {

 acc = [
  ...acc,
  [current.abv, current.population]
 ]

 return acc;
}, ["abv", "population"]);

Example: https://jsbin.com/gudivuhuro/edit?html,js,console

edited Oct 7, 2019 at 11:26

answered Oct 7, 2019 at 11:22

Ivor

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3 Comments

Igor Dymov Over a year ago

You could easily use ["abv", "population"] as an initial reducer value instead of an empty array

Ivor Over a year ago

@IgorDymov Agreed. Editing the answer.

Ivor Over a year ago

@Senelithperera I'm glad it helped, remember to 'accept' the answer that solved your question. 👍

Bilal Siddiqui · Accepted Answer · 2019-10-07 11:24:01Z

0

Seems your first data is static in desired output:

const columns = [
    {
      "usage": 395226,
      "population": 1925117,
      "value": 21,
      "abv": "MN"
    },
    {
      "usage": 893129,
      "population": 4327541,
      "value": 21,
      "abv": "IL"
    }
  ];
  
  let cols = [];
  if (columns.length) {
      cols.push(["abv", "population"]);
      columns.forEach(item => {
          cols.push([item.abv, item.population])
      });
  }
  console.log(cols);

answered Oct 7, 2019 at 11:24

Bilal Siddiqui

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Comments

Igor Dymov · Accepted Answer · 2019-10-07 11:31:16Z

0

I would end up using something like this:

const columns = [
    {
      "usage": 395226,
      "population": 1925117,
      "value": 21,
      "abv": "MN"
    },
    {
      "usage": 893129,
      "population": 4327541,
      "value": 21,
      "abv": "IL"
    }
];

let converted = columns.map((c) => [c.abv, c.population]);
converted.unshift(["abv", "population"]);

answered Oct 7, 2019 at 11:31

Igor Dymov

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Comments

zetawars · Accepted Answer · 2019-10-07 11:37:11Z

does this solve your problem ?

const columns = [
    {
      "usage": 395226,
      "population": 1925117,
      "value": 21,
      "abv": "MN"
    },
    {
      "usage": 893129,
      "population": 4327541,
      "value": 21,
      "abv": "IL"
    }
  ]
var k = [["abv", "population"]];
for(var i = 0; i < columns.length; i++){
    k.push([columns[i].abv, columns[i].population]);
}
console.log(k) // Expected expected output

and here is a generic Implementation if you so require that.

var names = ["abv", "population"];
var k = GetPropertiesInArray(columns, names); //[["abv", "population"]];

function GetPropertiesInArray(columns, names){
    var m = [];
    m.push(names);
    for(var i = 0; i < columns.length; i++){
        var item = [];
        for(var j in names){
            item.push(columns[i][names[j]]);
        }
        m.push(item);
    }

    return m;
}

console.log(k);//Expected output

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