JS regex matching ' but not \'

Question

I would like to replace the simple quotes in a string but not the escaped ones (in JavaScript). For example I want this string:

'Hello there! I\'m \'Doug\''

To become:

"Hello there! I\'m \'Doug\'"

NOTE: I made a lots of research and test (e.g on regex101.com) and found some things such as Regular expression to match a line that doesn't contain a word? but still can't figure out how to build a proper regex.

THINGS I TRIED:

/[^\\]'/g
/\\{0}'/g
/[\\]{0}'/g
...

`JS regex matching “ but not \”` but the input contains only single quotes. — Avinash Raj, Oct 03 '14 at 18:08
yep, he want to replace all the `'` except the one's which are preceded by a \ — Avinash Raj, Oct 03 '14 at 18:14
What should happen if the backslash before `'` is "escaped" with another backslash? — Oriol, Oct 03 '14 at 19:00
@Oriol good point! In my case the only character that can get escaped is the simple quote so `\\'` would stay `\\'`. In an other situation it would have become `\"` I guess. — Gabin, Oct 03 '14 at 19:05
possible duplicate of [PHP preg\_split ignore escaped sequence](http://stackoverflow.com/questions/16456055/php-preg-split-ignore-escaped-sequence) — CSᵠ, Oct 04 '14 at 01:19

score 1 · Accepted Answer · answered Oct 03 '14 at 18:49

1

You can use this String#replace with callback function:

str = "'Hello there! I\\'m \\'Doug\\''";
str = str.replace(/(\\)?'/g, function($0, $1) {
   return ($1) ? "\\'" : '"';
});
console.log( str );
//=> "Hello there! I\'m \'Doug\'"

answered Oct 03 '14 at 18:49

anubhava

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A bit weird and my strings doesn't contain a double \ to escape a simple quote. – Gabin Oct 03 '14 at 19:01
It is not double quote if you print it, it will show only single \ – anubhava Oct 03 '14 at 19:04
Yes sure but your original string contains a double backslash, not mine. My example is `'Hello there! I\'m \'Doug\''` not `'Hello there! I\\'m \\'Doug\\''` – Gabin Oct 03 '14 at 19:08
You're mistaken. Use `alert("'Hello there! I\'m \'Doug\''")` to see what gets printed. – anubhava Oct 03 '14 at 19:10
This is what I am trying to tell you. [See this jsfiddle](http://jsfiddle.net/mbwy757f/1/) and see what first `console.log(str)` prints i.e. no / in the output. – anubhava Oct 03 '14 at 19:20
The console does not print it but it still exist in the string. For example: http://jsfiddle.net/mbwy757f/2/ – Gabin Oct 03 '14 at 19:28
That is **exactly** what I have been saying. Creating string in Javascript will need double / but getting it from HTML will be fine with single /. **[See my working code here](http://jsfiddle.net/mbwy757f/3/)** which prints **`"I\'m doug!"`** – anubhava Oct 03 '14 at 19:31
1

My bad, you was right! It's actually a bit strange but now I get it :) Thank you very much for your time. – Gabin Oct 03 '14 at 20:11

score 0 · Answer 2 · answered Oct 03 '14 at 18:31

0

This is close:

subject.replace(/^'|([^\\])'/g, '$1"')

It won't catch two apostrophes in a row, but I suppose you could just run it twice.

answered Oct 03 '14 at 18:31

Jeremy Stein

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Thank you but what if the string contains X apostrophes? How much times will I have to run it? Seems like there is probably a best way to do this. – Gabin Oct 03 '14 at 18:40
If it contains X apostrophes, you'll have to run it twice. It will replace every other one. – Jeremy Stein Oct 03 '14 at 21:39

score 0 · Answer 3 · answered Oct 03 '14 at 18:56

0

Unfortunately, javascript besides all its portability and power doesn't support lookbehinds.

I made a regex to work well in the case of having multiple apostrophes too:

^'|[^\\](')[']+|([^\\])'

Replace with $1"

Online demo

answered Oct 03 '14 at 18:56

revo

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You're getting closer but `"Hello there! I\''''''m \'Doug\'"` should result in `"Hello there! I\'"""""m \'Doug\'"` – Gabin Oct 03 '14 at 18:59

score -1 · Answer 4 · answered Oct 03 '14 at 18:46

-1

Maybe you need just this:

var text = "'Hello there! I'm \'Doug\''"; 
text.replace(/^\'|'$/g, '"')

answered Oct 03 '14 at 18:46

speedy32

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JS regex matching ' but not \'

4 Answers4