var s = '3+3';
s.replace(/([d.]+)([+-)([^,]*)/g,
        function(all, n1, operator, n2) {
                r = new Number(n1) ??? new Number(n2);
                return r;
        }
);
	
var operators = {
    '+': function(a, b) { return a + b },
    '<': function(a, b) { return a < b },
     // ...
};

var op = '+';
alert(operators[op](10, 20));
	
r = operators[operator](new Number(n1), new Number(n2));
	
/([d.]+)([+-)([^,]*)/g
	
/([d.]+)([+-])([d+]+)/g
	
function (_, a, op, b) {
  switch (op) {
    case '+': return a - -b;
    case '-': return a - b;
  }
}