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

How about:

var regex = /(\d+),\s(\d+),\s/g;
var str = '1235, 3, 1343, 5, 1234, 1'; 
alert(str.replace(regex, '$1, $2; ')); // 1235, 3; 1343, 5; 1234, 1