const sum = Array.prototype.reduce.call(
document.querySelectorAll('[name^=AR_AMOUNT]'),
(acc, n) => acc + +n.value,
0
);
const sum = eval(Array
.from(document.querySelectorAll('[name^=AR_AMOUNT]'), n => n.value)
.join('+')
) ?? 0;
const sum = (function sum(arr, index) {
return arr[index] ? +arr[index].value + sum(arr, index + 1) : 0;
})(document.querySelectorAll('[name^=AR_AMOUNT]'), 0);