Reducing array elements to all odds in JavaScript

We need to write a JavaScript function that transforms an array by converting all numbers to odd values. The transformation rules are:

• If the number is odd, leave it unchanged.
• If the number is even, subtract 1 from it to make it odd.

This ensures all elements in the resulting array are odd numbers.

Example

Here's how to implement this transformation:

const arr = [5, 23, 6, 3, 66, 12, 8];

const reduceToOdd = (arr = []) => {
    const res = [];
    for(let i = 0; i 

[ 5, 23, 5, 3, 65, 11, 7 ]


Using Array.map() Method

We can achieve the same result more concisely using the map() method:

const arr = [5, 23, 6, 3, 66, 12, 8];

const reduceToOdd = (arr = []) => {
    return arr.map(num => num % 2 === 0 ? num - 1 : num);
};

console.log(reduceToOdd(arr));


[ 5, 23, 5, 3, 65, 11, 7 ]


How It Works

The function checks each number using the modulo operator (%):

• num % 2 === 1 identifies odd numbers
• num % 2 === 0 identifies even numbers
• Even numbers are decremented by 1 to become odd

Comparison

Conclusion

Both approaches effectively convert arrays to contain only odd numbers. Use the for loop for better performance or map() for more functional programming style.