Javascript: How to construct an object from several arrays and variables?

Question

I have 2 different sets of arrays which are needed to be merged into an object

x1 = ['US', 'UK', 'China'];
y1 = [1,2,3];
name1 = 'CO2';

x2 = ['US', 'UK', 'China'];
y2 = [4,5,6];
name2 = 'GHG';

x1 and x2 are always the same.

My ideal result


[{'country': 'US', 'CO2': 1, 'GHG': 2},
{'country': 'UK', 'CO2': 2, 'GHG': 5},
{'country': 'China', 'CO2': 3, 'GHG': 6}]

I have tried to construct an object like this

var result = {};

x1.forEach(function (key,i) { result.country = key, result[name1] = y1[i] });

but it returns only the last value

{country: "China", CO2: 3}

And like this

x1.forEach((key, i) => result[key] = y1[i]);

But then the name is out of the play

And the whole thing should be dynamic which also makes additional problems, I cannot manually set values like I needed.

You could do something like this: let result = x1.map((v,i)=>({"country":v, [name1]:y1[i], [name2]:y2[i]})) — ptothep
– ptothep, Commented Dec 4, 2020 at 8:16
are you sure that the value of GHG in {'country': 'US', 'CO2': 1, 'GHG': 2} is not a typo? — Alan Omar
– Alan Omar, Commented Dec 4, 2020 at 8:31

michael · Accepted Answer · 2020-12-04 08:12:16Z

4

const x1 = ['US', 'UK', 'China'];
const y1 = [1, 2, 3];
const name1 = 'CO2';

const x2 = ['US', 'UK', 'China'];
const y2 = [4, 5, 6];
const name2 = 'GHG';

const result = x1.map((country, index) => ({
  country,
  [name1]: y1[index],
  [name2]: y2[index]
}));

console.log(result);

answered Dec 4, 2020 at 8:12

michael

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Comments

Olivier Cartier · Accepted Answer · 2020-12-04 08:12:24Z

1

I think you can try something like this, basically, we go through x1 and build the result with the corresponding data.

var result = {}
for(i = 0; i < x1.length; i++) {
  result[i] = {}
  result[i]["country"] = x1[i]
  result[i][name1] = y1[i]
  result[i][name2] = y2[i]
}

console.log(result)

answered Dec 4, 2020 at 8:12

Olivier Cartier

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Comments

hemant kumar · Accepted Answer · 2020-12-04 08:21:46Z

1

You can do this like following(note : no need of variable x2)-

function createObj(x1,y1,y2, name1, name2){
  var obj1={},
         obj2={},
         obj3={};
  var result=[obj1, obj2, obj3];
  result.forEach((obj, i)=>{
    obj.country=x1[i];
    obj[name1]=y1[i];
    obj[name2]=y2[i];
  })

  return result;
  
}

In your code you are getting the last value only because every time inside the for each loop you override the values of the object

answered Dec 4, 2020 at 8:21

hemant kumar

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Comments

Alan Omar · Accepted Answer · 2020-12-04 08:28:47Z

1

let x1=["US","UK","China"],y1=[1,2,3],name1="CO2",x2=["US","UK","China"],y2=[4,5,6],name2="GHG";

let result = x1.map((e,idx) => ({country:x1[idx],co2:y1[idx],GHG:y2[idx]}))

console.log(result)

answered Dec 4, 2020 at 8:28

Alan Omar

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