arrayReduce.js

let data  = [
    {id: 1, title: 'Nite watch', price: 33, discount:0},
    {id: 2,  title: 'what I want', price: 12, discount:0.4},
    {id: 3, title: 'Mercy at last', price: 405, discount:0.25},
    {id: 4, title: 'Nothting between', price: 550, discount:0}
];
priceSum = data.reduce((acc, currentValue) => acc + currentValue.price, 0);
console.log(priceSum);
// console result
1000

priceSum = data.reduce((acc, currentValue) => acc + currentValue.price);
console.log(priceSum);

// console result
"[object Object]12405550"