Regular Expressions 101

Non-Capturing Group(?:(?:###)?([^# \n]+))

Non-Capturing Group(?:###)?

?repeats the group contents below at most once:

###the literal text ###

Group 1([^# \n]+)

Negated Character Class[^# \n]+

+matches at least one character outside the set below:

#the literal # (35₁₀ / 43₈ / 23₁₆)

the literal (32₁₀ / 40₈ / 20₁₆)

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

Positive Lookahead(?=$|(?:###[^# ]+)*[^\n]*?(http:\/\/[^\n]+))

1st Alternative$

$end of string, or before its final line terminator

2nd Alternative(?:###[^# ]+)*[^\n]*?(http:\/\/[^\n]+)

Non-Capturing Group(?:###[^# ]+)*

*repeats the group contents below any number of times:

###the literal text ###

Negated Character Class[^# ]+

+matches at least one character outside the set below:

#the literal # (35₁₀ / 43₈ / 23₁₆)

the literal (32₁₀ / 40₈ / 20₁₆)

Negated Character Class[^\n]*?

*?matches any number of characters outside the set below:

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

Group 2(http:\/\/[^\n]+)

http:the literal text http: (case sensitive)

\/the literal / (47₁₀ / 57₈ / 2F₁₆)

Negated Character Class[^\n]+

+matches at least one character outside the set below:

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

Non-Capturing Group(?: http:\/\/[^\n]+)?

?repeats the group contents below at most once:

http:the literal text http: (case sensitive)

\/the literal / (47₁₀ / 57₈ / 2F₁₆)

Negated Character Class[^\n]+

+matches at least one character outside the set below:

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

Global pattern flags

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

Detailed match information will be displayed here automatically.

Search reference

Regular Expression

(?:(?:###)?([^# \n]+))(?=$|(?:###[^# ]+)*[^\n]*?(http:\/\/[^\n]+))(?: http:\/\/[^\n]+)?

Test String
New

a1@zjmainstay.cn###a2@zjmainstay.cn###a3@zjmainstay.cn http://www.zjmainstay.cn/my-regexp
a1@zjmainstay.cn###a2@zjmainstay.cn###a3@zjmainstay.cn###a4@zjmainstay.cn###a5@zjmainstay.cn http://www.zjmainstay.cn/deep-regexp

Regular Expression

Test StringNew

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Test String
New

Extraction
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