JSFiddle - React, Tailwind, and code Playground
JavaScript
/* var str = "(1,2),(3,4),(5,6)"; */
var str = '(4, 5, 3, 6), (6, 2, 3, 5), (9, 3, 4, 5), (1, 4, 5, 2)';
var idx = -1,
sum = 1;
do {
var idx = str.indexOf('(', idx + 1);
var num = str.substr(idx + 4, 1); console.log(num);
if (!isNaN(num)) {
sum = sum * num;
}
} while (idx > -1)
console.log(sum);