" between every pair of 'ab' or 'ba', for example:

Question

but it doesn't work in Safari, because it doesn't support positive lookbehind.

(?<=a)(?=b)|(?<=b)(?=a)

Is there an alternative way to change this regular expression so it can work in Safari?

ab -> a|b
aba -> a|b|a
ababa -> a|b|a|b|a
aaabbbaaabaaaaaab -> aaa|bbb|aaa|b|aaaaaa|b

(?<=a)(?=b)