What regex flavor does Notesnook use?#

Notesnook’s regex engine is based on
JavaScript (ECMAScript) flavor. Since Notesnook is a cross-platform app built using modern web technologies (React Native), it is consistent with how JavaScript handles regular expressions.
Key features of the JavaScript regex flavor

• Case-sensitivity: By default, it is case-sensitive, though this can be toggled in the Find and Replace dialog.
• Multiline mode (m flag): In JavaScript regex, the m flag makes the ^ and $anchors match the start and end of each line rather than the start and end of the entire string.
• Line breaks: The escape sequence is used for a new line, but its interpretation can depend on the operating system. Using the actual line break character in the “Replace” field is a robust workaround if doesn’t work as expected.
• Capture groups: Standard parentheses () create a capture group, and these can be referenced in the replacement string using $1, $2, etc..
• Lookaheads and lookbehinds: JavaScript regex supports both positive lookaheads (?=...) and negative lookaheads (?!...). While lookbehinds (?<=...) were not available in older versions, they are supported in newer ECMAScript standards.

Why might not work in the “Replace” field
The primary reason for the issue is that some text editor replacement fields do not process escape characters like directly. Instead, they require a literal new line.

• When you type in a replacement box, the editor may treat it as the two literal characters \ and n, not as a command for a new line.
• The workaround of copying a literal new line character and pasting it into the “Replace” field directly inserts the character the engine expects, bypassing any need for escape character interpretation in that context.