Regex to remove all instance of letter outside of quotes - regex

Question

I have a string of text:
\n new"test \n aaaa" \n ta \n `this is a \n newline that should be kept`
My goal is to match all \n's outside of backticks (`), quotes ("), or single quotes ('). Based off another question (https://stackoverflow.com/a/48953880/14465957), I switched the positive lookahead used to a negative one, which now matches all newlines outside of quotes ("). However, it doesn't work when I attempted to ignore single and back ticks.
What am I doing wrong?
Working quotes:
https://regex101.com/r/ooqz5d/1/

Answer 1

If you're using PCRE, you can use a control verb to skip everything inside of a quote closure:
(['"`]).*?\1(*SKIP)(*F)|\\n
(['"`]) any type of quote, put it in group 1
.*? any characters, non greedy
\1 the quote that captured in group 1
(*SKIP)(*F) skip the current match, which is a quote closure
|\\n match a \n
See the test cases
Also, if you need to ignore escaped quotes(\", \' etc), you may try
(['"`])(?:(?<!\\)\\(?:\\\\)*\1|(?!\1).)*\1(*SKIP)(*F)|\\n
Check the test cases
Using JavaScript
For JavaScript, you can't use control verbs. But you can use group capture to replace outbound \n
Regex
((['"`])[\s\S]*?\2)|\\n
Substitution
$1
const regex = /((['"`])[\s\S]*?\2)|\\n/g;
const text = String.raw`\nnew"test\naaaa"\nta\n\`this is a \nnewline that should be kept\`\ntest\n'this \n should also be kept'\n`;
console.log('before\n', text);
const result = text.replace(regex, '$1');
console.log('after\n', result);
Real line breaks
const regex = /((['"`])[\s\S]*?\2)|\n/g;
const text = `\nnew"test\naaaa"\nta\n\`this is a \nnewline that should be kept\`\ntest\n'this \n should also be kept'\n`;
console.log('before\n----\n', text);
const result = text.replace(regex, '$1');
console.log('after\n----\n', result);

Answer 2

Use
text.replace(/("[^"\\]*(?:\\.[^"\\]*)*"|'[^'\\]*(?:\\.[^'\\]*)*'|`[^`\\]*(?:\\.[^`\\]*)*`)|\\n/g, '$1')
See regex proof.
EXPLANATION
--------------------------------------------------------------------------------
( group and capture to \1:
--------------------------------------------------------------------------------
" '"'
--------------------------------------------------------------------------------
[^"\\]* any character except: '"', '\\' (0 or
more times (matching the most amount
possible))
--------------------------------------------------------------------------------
(?: group, but do not capture (0 or more
times (matching the most amount
possible)):
--------------------------------------------------------------------------------
\\ '\'
--------------------------------------------------------------------------------
. any character except \n
--------------------------------------------------------------------------------
[^"\\]* any character except: '"', '\\' (0 or
more times (matching the most amount
possible))
--------------------------------------------------------------------------------
)* end of grouping
--------------------------------------------------------------------------------
" '"'
--------------------------------------------------------------------------------
| OR
--------------------------------------------------------------------------------
' '\''
--------------------------------------------------------------------------------
[^'\\]* any character except: ''', '\\' (0 or
more times (matching the most amount
possible))
--------------------------------------------------------------------------------
(?: group, but do not capture (0 or more
times (matching the most amount
possible)):
--------------------------------------------------------------------------------
\\ '\'
--------------------------------------------------------------------------------
. any character except \n
--------------------------------------------------------------------------------
[^'\\]* any character except: ''', '\\' (0 or
more times (matching the most amount
possible))
--------------------------------------------------------------------------------
)* end of grouping
--------------------------------------------------------------------------------
' '\''
--------------------------------------------------------------------------------
| OR
--------------------------------------------------------------------------------
` '`'
--------------------------------------------------------------------------------
[^`\\]* any character except: '`', '\\' (0 or
more times (matching the most amount
possible))
--------------------------------------------------------------------------------
(?: group, but do not capture (0 or more
times (matching the most amount
possible)):
--------------------------------------------------------------------------------
\\ '\'
--------------------------------------------------------------------------------
. any character except \n
--------------------------------------------------------------------------------
[^`\\]* any character except: '`', '\\' (0 or
more times (matching the most amount
possible))
--------------------------------------------------------------------------------
)* end of grouping
--------------------------------------------------------------------------------
` '`'
--------------------------------------------------------------------------------
) end of \1
--------------------------------------------------------------------------------
| OR
--------------------------------------------------------------------------------
\\ '\'
--------------------------------------------------------------------------------
n 'n'
JavaScript code:
const text = String.raw`\nnew"test\naaaa\\\n"\nta\n\`this is a \nnewline that should be kept\`\n'this is a \nnew test'\n`
console.log(text.replace(/("[^"\\]*(?:\\.[^"\\]*)*"|'[^'\\]*(?:\\.[^'\\]*)*'|`[^`\\]*(?:\\.[^`\\]*)*`)|\\n/g, '$1'))