Solution is good, I would suggest using more descriptive names (obviously codewars isn't exactly nudging us in the right direction with parameter names like "s").

For example: "s1" and "s2" tell us nothing about the variables - something like "capitalizedAtEven" and "capitalizedAtOdd" would be clearer (although still not perfect).

Good catch!

You can work around this by escaping all special characters in the string before passing it to the RegExp constructor. Sadly, there's no built-in way to do this, you can make a function like this:

RegExp.prototype.escape = function(string) {
return string.replace(/[-/\^$*+?.()|[]{}]/g, '\$&')
};