JavaScript - sum only negative numbers in array

In this article, we would like to show you how to sum only negative numbers in array using JavaScript.

Quick solution:

// ONLINE-RUNNER:browser;

var numbers = [-1, -2, -3, 4, 5, 6];

var result = 0;

for (var i = 0; i < numbers.length; ++i) {
    if (numbers[i] < 0) {
        result += numbers[i];
    }
}

console.log(result); // -6

Practical example

In this example, we create a reusable arrow function that checks if a number is negative and sums it up.

// ONLINE-RUNNER:browser;

const sumNegative = (numbers) => {
    let result = 0;
    for (let i = 0; i < numbers.length; ++i) {
        if (numbers[i] < 0) {
            result += numbers[i];
        }
    }
    return result;
};


// Usage example:

const result = sumNegative([-1, -2, -3, 4, 5, 6]);

console.log(result); // -6