Regular Expressions 101

1st Alternative(\d{1,2}\/\d{1,2}\/\d{4})\n

Group 1(\d{1,2}\/\d{1,2}\/\d{4})

\d{1,2}a digit, repeated between 1 and 2 times

\/the literal / (47₁₀ / 57₈ / 2F₁₆)

\d{1,2}a digit, repeated between 1 and 2 times

\/the literal / (47₁₀ / 57₈ / 2F₁₆)

\d{4}a digit, repeated exactly 4 times

\na line-feed (newline) character (ASCII 10)

2nd Alternative((?:(?!\n*\d{1,2}\/\d{1,2}\/\d{4})[\s\S])+)

Group 2((?:(?!\n*\d{1,2}\/\d{1,2}\/\d{4})[\s\S])+)

Non-Capturing Group(?:(?!\n*\d{1,2}\/\d{1,2}\/\d{4})[\s\S])+

+repeats the group contents below at least once:

Negative Lookahead(?!\n*\d{1,2}\/\d{1,2}\/\d{4})

\n*a line-feed (newline) character (ASCII 10), repeated any number of times

\d{1,2}a digit, repeated between 1 and 2 times

\/the literal / (47₁₀ / 57₈ / 2F₁₆)

\d{1,2}a digit, repeated between 1 and 2 times

\/the literal / (47₁₀ / 57₈ / 2F₁₆)

\d{4}a digit, repeated exactly 4 times

Character Class[\s\S]

\sany whitespace character

\Sany non-whitespace character

Global pattern flags

g modifier: global. Finds all matches instead of stopping after the first

i modifier: insensitive. Matches without distinguishing uppercase and lowercase letters

m modifier: multiline. Causes ^ and $ to match the start and end of each line, not only the start and end of the string

Detailed match information will be displayed here automatically.

Search reference

Regular Expression

(\d{1,2}\/\d{1,2}\/\d{4})\n|((?:(?!\n*\d{1,2}\/\d{1,2}\/\d{4})[\s\S])+)

New

1/12/2011
I did something.

10/5/2013
I did something else.

Here is another line.

And another.

5/17/2014
Lalala.
More text on another line.