regex101: JavaScript Substitution Workspace

Pro

Positive Lookahead(?=^\d{1,2}\/\d{1,2}\/\d{4})

^start of line

\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

Global pattern flags

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

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

26 tokens

Regular Expression

(?=^\d{1,2}\/\d{1,2}\/\d{4})

New

18/07/2018, 18:04 - Person2: message
18/07/2018, 18:04 - Person1: Yes
18/07/2018, 18:04 - Person2: That's good then
18/07/2018, 18:05 - Person1: message line 1
 message line 2
18/07/2018, 18:05 - Person2: text
18/07/2018, 18:05 - Person2: But nvm
18/07/2018, 18:06 - Person1: text

Extraction

18/07/2018, 18:04 - Person2: message
18/07/2018, 18:04 - Person1: Yes
18/07/2018, 18:04 - Person2: That's good then
18/07/2018, 18:05 - Person1: message line 1
 message line 2
18/07/2018, 18:05 - Person2: text
18/07/2018, 18:05 - Person2: But nvm
18/07/2018, 18:06 - Person1: text