How to make this positive lookbehind regular expression run in Safari

user_2731640 0
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(?<=a)(?=b)|(?<=b)(?=a)

I use this regex to insert a "|" between every pair of 'ab' or 'ba', for example:

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

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

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

safari javascript regex
2 Answers

You may use

.replace(/(a)(?=b)|(b)(?=a)/g, '$1$2|')

See the regex demo online.

Details

  • (a)(?=b) - matches and captures a into Group 1 if there is b immediately on the right
  • | - or
  • (b)(?=a) - matches and captures b into Group 2 if there is a immediately to the right of the current location.

The replacement is Group 1 + Group 2 vaues (only one of them will be populated with text upon a match) and a | char.

See the JS demo below:

var rx = /(a)(?=b)|(b)(?=a)/g;
var strs = ['aba', 'abab', 'aaabbbababab'];
for (var s of strs) {
   console.log(s, '=>', s.replace(rx, '$1$2|'));
}

user_38329700

Lookarounds are not needed here. We can just do two separate greedy replacements for ab and ba:

var input = "aaabbbaaabaaaaaab";
var output = input.replace(/ab/g, "a|b").replace(/ba/g, "b|a");
console.log(output);

user_18632290
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