Question

I have to remove a set of lines that start with a marker and end with another marker.
I want to find all such pieces of text and remove them using regex. The problem is, regex only matches one line at a time. How should I proceed?

Answer 1

In most regex parsers, you can add a s to the end as a “dotall” modifier. This will make . match anything, including newlines (which it normally does not match).

But the dotall modifier does not exist in javascript. Instead, you have a “pseudo-dotall” modifier by using a predefined character class and its negation — collectively these two things will match anything, including a newline. The canonical example is [\s\S] (match anything that is whitespace or anything this is not whitespace = match anything). But any character class and its negation will do (e.g. [\d\D] will also work).

So in your case, if your start token is S and your end token is E you can do this:

string.replace(/S[\s\S]*?E/g, '')

Two notes: I am using the g or global modifier to replace all instances. And in [\s\S]*?, the ? means “match the shortest sequence” (non-greedy). That way it really will be instances of delimited tokens rather than treating all the stuff between the first begin token and last end token as a single token.