Javascript: How to reconstruct a nested object into another object?

Question

I have the following nested object:

var test = {'a': {'name': 'CO2', 'x': ['US', 'UK', 'China'], 'y': [1,2,3]}, 
            'b': {'name': 'GHG', 'x': ['US', 'UK', 'China'], 'y': [4,5,6]}
           };

I have to dynamically iterate and get the ideal result:

[{'country': 'US', 'CO2': 1, 'GHG': 4},
{'country': 'UK', 'CO2': 2, 'GHG': 5},
{'country': 'China', 'CO2': 3, 'GHG': 6}]

I have already asked but it was the thing with arrays and I can't get how to work with objects.

I can iterate and get an array of 2 objects but it is not what I needed

var traces = [];

Object.keys(test).forEach(function(key) { 
  var keys = test[key].x;
  var values = test[key].y;
  var name = test[key].name;


  var trace = keys.map((country, index) => ({
     country,
     [name]: values[index]

  }));

traces.push(trace);
});

adiga · Accepted Answer · 2020-12-07 05:50:04Z

2

You could reduce the values of the test object. Add each country as a key to the accumulator object and the object needed in the output as its value. Loop through each country in x and update the accumulator.

const test={a:{name:"CO2",x:["US","UK","China"],y:[1,2,3]},b:{name:"GHG",x:["US","UK","China"],y:[4,5,6]}},

    values = Object.values(test),
  
    group = values.reduce((acc, { name, x, y }) => {
      x.forEach((country, i) => {
        acc[country] ||= { country }
        acc[country][name] = y[i]
      })
      return acc
    }, {}),
    
    output = Object.values(group)

console.log(output)

answered Dec 7, 2020 at 5:50

adiga

35.4k9 gold badges66 silver badges88 bronze badges

Sign up to request clarification or add additional context in comments.

5 Comments

KcH Over a year ago

great solution @adiga .... please could you explain this line acc[country] ||= { country } i'm learning from answers :)

adiga Over a year ago

@Codenewbie It's using the Logical OR assignment and Shorthand property names. It's equivalent to acc[country] = acc[country] || { "country": country }. The goal is to create an accumulator object is like { US: { country: "US", 'CO2': 1 } }. If the accumulator object doesn't have US as key, add the key and set it to { country: 'US' }

KcH Over a year ago

@adiga Wow they are amazing and very handy, tysm for explaining gbu :) ... :)

adiga Over a year ago

@Codenewbie there are two more similar conditional assignment operators AND &&= and Nullish assignment ??=. So, let a = null; a ??= 'value' will assign a new value to a only if a is null or undefined.

KcH Over a year ago

@adiga just saw all of them bro :) thanks for mentioning .... so kind of you

Collectives™ on Stack Overflow

Javascript: How to reconstruct a nested object into another object?

1 Answer 1

5 Comments

Your Answer

Hot Network Questions

Collectives™ on Stack Overflow

1 Answer 1

5 Comments

Your Answer

Sign up or log in

Post as a guest

Related