Smart String Replacements

Question

This works well for case insensitive replacements:

str = str.replace(new RegExp(phrase, 'gi'), '<span style="color:red;">' + phrase + '</span>');

But what I do want is to not change case when replaced which above-mentioned does.

Answer 1

Capture the phrase with parenthesis, and use $1 in the replace string, eg:

'Foobar'.replace(/(foo)/gi, '<x>$1</x>')

Would result in <x>Foo</x>bar

Answer 2

str = str.replace(new RegExp(phrase, 'gi'), '<span>$&</span>');