javascript replace string with exact match

Question

i have bulk of email address in textarea 'test1@hotmail.comtest2@outlook.com.mytest3@outlook.comtest4@hotmail.com.mytest5@hotmail.com.mytest6@hotmail.com'

what i want to do is add 'comma space' behind of .com / .com.my

expected result after onblur function in textarea: `test1@hotmail.com, test2@outlook.com.my, test3@outlook.com, test4@hotmail.com.my, test5@hotmail.com.my, test6@hotmail.com

what i have tried.

b = value.split('.com.my').join('.com.my, ');
b = value.split('.com').join('.com, ');

problem : it will replace all '.com' to '.com, ' even with '.com.my'

Answer 1

var value = "test1@hotmail.comtest2@outlook.com.mytest3@outlook.comtest4@hotmail.com.mytest5@hotmail.com.mytest6@hotmail.com";
value = value.replace(/(.com(.my)?)/gm, '$1, ');
console.log(value.substring(0, value.length - 2));