JavaScript - sum property values in array of objects

In this article, we would like to show you how to sum property values in an array of objects in JavaScript.

Quick solution:

// ONLINE-RUNNER:browser;

const sumProperty = (array, property) => {
    return array.reduce((a, b) => a + (b[property] || 0), 0);
};


// Usage example:

const items = [
    { name: 'item1', quantity: 1 },
    { name: 'item2', quantity: 2 },
    { name: 'item3', quantity: 3 },
];

console.log(sumProperty(items, 'quantity')); // 6

Creating class with sum() method

In this example, we create ItemsCollection class with sum() method that sums the quantity of items.

// ONLINE-RUNNER:browser;

class ItemsCollection extends Array {
    sum(property) {
        return this.reduce((a, b) => a + (b[property] || 0), 0);
    }
}
const items = new ItemsCollection(...[
   { name: 'item1', quantity: 1 },
   { name: 'item2', quantity: 2 },
   { name: 'item3', quantity: 3 },
]);

console.log(items.sum('quantity')); // 6

References

1. Array.prototype.reduce() - JavaScript | MDN