Help with regexp replacing every second comma in the string

Question

I have a string of that displays like this....

1235, 3, 1343, 5, 1234, 1

I need to replace every second comma with a semicolon

i.e.

1235, 3;

Answer 1

var foo = "1235,3,1343,5,1234,1".replace(/(.\*?),(.\*?),/g, "$1,$2;");

console.log(foo)