Text Processing with JavaScript

Recipe 42

Forcing . to Match Newline Characters with the s Flag

Task

Suppose you want to write a script that removes all comments from JavaScript files to reduce their file size. Removing single-line comments is easy: just find a line that starts with double forward slashes and delete the entire line.

But removing block comments with the /* */ syntax that may span multiple lines is a bit trickier. You might expect a pattern like /\/\*.*\*\// to work because it finds a /* followed by any character until it reaches */.

But, the full stop token in this pattern won’t match line break characters, so the regex could fail:

part_2/flag_dotall/dotall_ex1.js

const re = /\/\*.*?\*\//;

const comment = `/* this
is a multiline
comment ...