Inverting signs of integers in an array using JavaScript

Problem

We are required to write a JavaScript function that takes in an array of integers (negatives and positives).

Our function should convert all positives to negatives and all negatives to positives and return the resulting array.

Method 1: Using for Loop

The traditional approach uses a for loop to iterate through each element and multiply by -1 to invert the sign:

const arr = [5, 67, -4, 3, -45, -23, 67, 0];

const invertSigns = (arr = []) => {
    const res = [];
    for(let i = 0; i < arr.length; i++){
        const el = arr[i];
        if(+el && el !== 0){
            const inverted = el * -1;
            res.push(inverted);
        } else {
            res.push(el);
        }
    }
    return res;
};

console.log(invertSigns(arr));

[ -5, -67, 4, -3, 45, 23, -67, 0 ]

Method 2: Using map() Method

A more concise approach using the array map() method:

const arr = [5, 67, -4, 3, -45, -23, 67, 0];

const invertSigns = (arr = []) => {
    return arr.map(num => num === 0 ? 0 : -num);
};

console.log(invertSigns(arr));

[ -5, -67, 4, -3, 45, 23, -67, 0 ]

Method 3: Simplified Approach

Since multiplying by -1 handles zero correctly (returns -0 which equals 0), we can simplify further:

const arr = [5, 67, -4, 3, -45, -23, 67, 0];

const invertSigns = (arr = []) => {
    return arr.map(num => -num);
};

console.log(invertSigns(arr));

[ -5, -67, 4, -3, 45, 23, -67, 0 ]

Comparison

Conclusion

The simplest approach using arr.map(num => -num) is the most readable and concise. All methods produce the same result, with positive numbers becoming negative and vice versa.