strojopis součet všech prvků v poli
const sum = receiptItems.reduce((sum, current) => sum + current.total, 0);
jak najít součet pole pomocí Javascriptu
// If you do not want to use array.reduece you can itereate through the array and then get the solution.
const getSum = (arr)=>{
let sum = 0;
for(key of arr){
sum += key
}
return sum
}