CODEWITHSUNDEEP
javascriptarraysobjectreduce
Andres Blanco
Andres Blanco

Reputation: 11

Reducing an array of objects into a single object with its values being a concatenation of the values from the old array

I have an array of objects that I want to reduce into a single object. The sample array always has the same keys in each of its objects as seen below:

sample = [
    {australia: 0, belgium: 0, brazil: 0, canada: 1, china: 1, ...},
    {australia: 0, belgium: 0, brazil: 3, canada: 2, china: 2, ...},
    {australia: 2, belgium: 1, brazil: 4, canada: 2, china: 5, ...}
]

I am looking to obtain a single object where the keys are the same as in the objects, and the values are a concatenation of each value in the initial array. Something like this:

desiredResult: {australia:[0,0,2],belgium:[0,0,1],brazil:[0,3,4],canada:[1,2,2],china:[1,2,5],...}

So far I have been trying the following reduce method on the array, but I am missing the part where I concatenate all the values:

let desiredResult = sample.reduce((a,b) =>({...a, desiredResult: b}),{})

// Which results in:
// desiredResult: {australia: 2, belgium: 1, brazil: 4, canada: 2, china: 5}

¿Could you help me figure out the best way to reach this solution?

Upvotes: 0

Views: 285

Answers (3)

Rajneesh
Rajneesh

Reputation: 5308

You can try reduce by taking entries of element in key, value form and then pushing them using for..of in accumulator accordingly:

var sample = [{ australia: 0, belgium: 0, brazil: 0, canada: 1, china: 1 }, { australia: 0, belgium: 0, brazil: 3, canada: 2, china: 2 }, { australia: 2, belgium: 1, brazil: 4, canada: 2, china: 5 }]
    
const result= sample.reduce((acc, elem)=>{
    countries= Object.entries(elem); 
    for(const [country, count] of countries){
    	  acc[country]= acc[country] || [];
    	  acc[country].push(count);
    	}
    	return acc;
},{});
console.log(result);

Upvotes: 0

brk
brk

Reputation: 50291

Since each of the lement in the array is again a object , you need to iterate them

let sample = [{
    'australia': 0,
    'belgium': 0,
    'brazil': 0,
    'canada': 1,
    'china': 1
  },
  {
    'australia': 0,
    'belgium': 0,
    'brazil': 3,
    'canada': 2,
    'china': 2
  },
  {
    'australia': 2,
    'belgium': 1,
    'brazil': 4,
    'canada': 2,
    'china': 5
  }
];

let newData = sample.reduce((acc, curr) => {
  for (let keys in curr) {
    if (!acc[keys]) {
      acc[keys] = []
    }
    acc[keys].push(curr[keys])
  }
  return acc;
}, {});

console.log(newData)

Upvotes: 1

Nina Scholz
Nina Scholz

Reputation: 386550

You could get the entries and create new properties as array and push the value to it.

var sample = [{ australia: 0, belgium: 0, brazil: 0, canada: 1, china: 1 }, { australia: 0, belgium: 0, brazil: 3, canada: 2, china: 2 }, { australia: 2, belgium: 1, brazil: 4, canada: 2, china: 5 }],
    result = sample.reduce((r, o) => {
        Object.entries(o).forEach(([k, v]) => (r[k] = r[k] || []).push(v));
        return r;
    }, {});

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

Upvotes: 1

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