CODEWITHSUNDEEP
javascriptarraysfunctionobjectreduce
Ian Hecht
Ian Hecht

Reputation: 27

How to use reduce to return an object in Javascript?

I'm trying to count the number of odd and even numbers in an array by using the Array.reduce() method. When I run the below code, I get the error "odd is not defined." How/where do I define odd to get this code to work?

var numbers = [5, 3, 8, 6, 9, 1, 0, 2, 2];
var oddEvenCounts = numbers.reduce(function(counts, number) {
   if (number % 2 === 1) {
     counts[odd]++
   } else {
     counts[even]++;
   }
   return counts;
 }, {});

Upvotes: 1

Views: 8301

Answers (3)

Rajat Gupta
Rajat Gupta

Reputation: 1

Answer using ES6+

const sumEvenOdd = (numbersArray) => {
    return numbersArray.reduce((acc, current) => current % 2 === 0 ? {...acc,'even':acc['even'] + current} : {...acc, 'odd':acc['odd'] + current}, {"even":0, "odd":0})
}'

console.log(sumEvenOdd([1, 6, 8, 5, 3]));
// Expected results: {even: 14, odd: 9}

Upvotes: 0

yaas
yaas

Reputation: 144

This is a function that can do it for you.

function oddEvenCounts(arr) {
  const counts = {
    even: 0,
    odd: 0
  };
  arr.forEach(n => {
    if(n % 2 === 0) {
      counts.even++;
    } else {
      counts.odd++
    }
  });
  return counts;
}

const array = [5, 3, 8, 6, 9, 1, 0, 2, 2];
console.log(oddEvenCounts(array));

Upvotes: 1

dork
dork

Reputation: 4568

Well, odd isn't defined. What you should do is either put odd/even in quotes (counts['odd']) or use dot notation (counts.odd).

Also, since odd and even aren't defined, incrementing them would result into NaN. The initial value should instead be { odd: 0, even: 0 }.

var numbers = [5, 3, 8, 6, 9, 1, 0, 2, 2];
var oddEvenCounts = numbers.reduce(function(counts, number) {
   if (number % 2 === 1) {
     counts['odd']++;
   } else {
     counts['even']++;
   }
   return counts;
 }, { odd: 0, even: 0 });
 
 console.log(oddEvenCounts);

Upvotes: 9

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