how to use nested arrays to form objects in javascript using the first array as object and the rest of the array as value

Question

I was given an array such as this :

data = [
  ['first_name', 'second_name', 'sex'],
  ['Jacob', 'David', 'M'],
  ['Kathryn', 'Gardener', 'F'],
  ['Jamaal', 'Dave', 'Unknown']
].

the solution is to return the array as an object looking something like this :

[
  { first_name: "Jacob", second_name: "David", sex: "M" },
  { first_name: "Kathryn", second_name: "Gardener", sex: "F" }
  {....}
];

I wrote the following code :

var object = {};
var arrays = [];
for (i = 0; i < data.length; i++){
   for (var j = i; j < data.length; j++){
       var keys = data[0][i];
       var values = data [j][i];
       object[keys] = values;
   }
   arrays.push(object);
};

but the output I'm having is :

[
   { 
      first_name :'Jamaal',
      second_name : 'Dave',
      sex : 'unknown'
   },
   { 
      first_name :'Jamaal',
      second_name : 'Dave',
      sex : 'unknown'
   },
   {
      first_name :'Jamaal',
      second_name : 'Dave',
       sex : 'unknown'
   },
   {
      first_name :'Jamaal',
      second_name : 'Dave',
      sex : 'unknown'
    }
];

I've also tried several ways either i end up with being able to create only one object...

Start your iteration loop from 1 not 0. And use data[0][i] as a keys. — oliver.voron
– oliver.voron, Commented Dec 3, 2019 at 11:58
Every index in the output array will point to the same var object = {}; — adiga
– adiga, Commented Dec 3, 2019 at 12:00

Nina Scholz · Accepted Answer · 2019-12-03 12:11:50Z

You need new object (references) inside of the first loop, otherwise you get the same object for every row.

var data = [ ['first_name', 'second_name', 'sex'], ['Jacob', 'David', 'M'], ['Kathryn', 'Gardener', 'F'], ['Jamaal', 'Dave', 'Unknown']],
    result = [],
    i, j,
    object;

for (i = 0; i < data.length; i++) {
    object = {};                           // take a new object
    for (j = 0; j < data[i].length; j++) { // start from zero
        object[data[0][j]] = data[i][j];   // use j as last key
    }
    result.push(object);
}

console.log(result);

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

A shorter approach with Object.fromEntries.

const
    getObjects = ([header, ...data]) => data.map(values =>
        Object.fromEntries(values.map((value, index) => [header[index], value])));

var data = [['first_name', 'second_name', 'sex'], ['Jacob', 'David', 'M'], ['Kathryn', 'Gardener', 'F'], ['Jamaal', 'Dave', 'Unknown']],
    result = getObjects(data);

console.log(result);

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

Jatin Parmar · Accepted Answer · 2019-12-03 11:59:34Z

2

you can do something like this

dataToObj=(data)=>{
   let head=data[0];
   let result=[];
   for(let i=1;i<data.length;i++){
      let obj={};
       for(let j=0;j<head.length;j++){
         obj[head[j]]=data[i][j]
       }
     result.push(obj);
 }
 return result;
}

answered Dec 3, 2019 at 11:59

Jatin Parmar

2,9596 gold badges22 silver badges34 bronze badges

Comments

Mohit Sahu · Accepted Answer · 2019-12-03 12:03:30Z

2

    var data = [
  ['first_name', 'second_name', 'sex'],
  ['Jacob', 'David', 'M'],
  ['Kathryn', 'Gardener', 'F'],
  ['Jamaal', 'Dave', 'Unknown']
]


function createObject(arr){
    var arr2 = [];
    keysArr = arr[0];
    arr.splice(0,1);
    arr.forEach(function(x,i){
        arr2[i] = {};
        arr[i].forEach(function(y,j){
            arr2[i][keysArr[j]] = arr[i][j];
        });
    });
    return arr2;
}

createObject(data);

answered Dec 3, 2019 at 12:03

Mohit Sahu

1772 silver badges17 bronze badges

Comments

PEPEGA · Accepted Answer · 2019-12-03 12:38:03Z

1

Since no one have posted a example with map i might as well do that, it's short and sweet!

var data = [['first_name', 'second_name', 'sex'],['Jacob', 'David', 'M'],['Kathryn', 'Gardener', 'F'],['Jamaal', 'Dave', 'Unknown']]

var res = []
data.slice(1).map((x, i) => {
  var obj = {}
  x.map((c, j) => {
    obj[data[0][j]] = x[j]
  })
  res.push(obj)
})

console.log(res)

edited Dec 3, 2019 at 12:38

answered Dec 3, 2019 at 12:30

PEPEGA

2,28027 silver badges42 bronze badges

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