This is part of the Semicolon&Sons Code Diary - consisting of lessons learned on the job. You're in the regex category.
Last Updated: 2024-12-03
The following Regex, built from a string, was not matching at all:
const regex = new RegExp(`${trackingCookieName}=(\w+)`)
The issue was that a single backslash in a string is ignored and removed by the interpreter.
"\w"
=> "w"
"\c\d\e"
=>"cde"
// But note that some special characters don't even print characters when backslashed
"\f"
""
"\n"
"
"
The JavaScript fix is to double backslash
const regex = new RegExp(`${trackingCookieName}=(\\w+)`)
This is true in other languages too - e.g. Ruby has the same behavior.
When converting a string to a regex, don't forget to double backslash.