Lookaheads are one of the most powerful feature in regular expressions. Lookaheads helps you to broaden your matches. You really may need to depend on these lookaheads in many scenarios. For instance, if you want to match every “N” in the paragraph which is not followed by a “O” . You cannot use the not (^) , say /N[^O]/ as it will match the second character also. So...
Lookahead and Lookbehind in regex tutorial
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