Javascript regex seems to add backslash to replacement

Question

I have a textearea called note_text, a div called note_preview and this function:

function fence_math(text) {
    return text
        .replace(new RegExp('\\\((.*?)\\\)', 'g'), '`memviv-math $1`')
        .replace(new RegExp('\\\[(.*?)\\\]', 'g'), '`memviv-equation $1`');
}

If I run this:

note_preview.innerHTML = fence_math(note_text.value);

When note_text contains

\(a *b* c\)

I get

<div id="note_preview">\`memviv-math a *b* c\`</div>

Why are there backslashes before the accents ? I would have expected:

<div id="note_preview">`memviv-math a *b* c`</div>

What can I do to get the proper result ?

Maybe because you are serializing a string and you cannot begin another string within a string? — Mr. Polywhirl, Oct 07 '20 at 18:00
Could you help me fix it ? I don’t see why the accent is not considered as a regular character. — vkubicki, Oct 07 '20 at 18:55

score 0 · Accepted Answer · answered Oct 07 '20 at 19:01

0

When you get value from the input it escaping special characters / in your case that's why your note_text.value is "\\(a *b* c\\)". Try to add extra backslashes to escape to your RegExp functions

.replace(new RegExp('\\\\((.*?)\\\\)', 'g'), '`memviv-math $1`')
.replace(new RegExp('\\\\[(.*?)\\\\]', 'g'), '`memviv-equation $1`');

answered Oct 07 '20 at 19:01

ukr.svyat

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Thank you, I forgot that Javascript escaped characters in strings. '\\\\\\((.*?)\\\\\\)' solved my problem. – vkubicki Oct 07 '20 at 19:22
No problem. You could mark that answer as accepted if it helped) – ukr.svyat Oct 07 '20 at 19:26
No need for another answer, it is already [172nd post](https://stackoverflow.com/questions/linked/17863066?lq=1) on the same topic. Please consider removing it. – Wiktor Stribiżew Oct 07 '20 at 20:09

Javascript regex seems to add backslash to replacement

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