Regular
Expressions
101
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Explanation
/
\.
(?!
html
?
)(
[
a
-
z
]
{0,3}
|
[
a
-
z
]
{0,4}
)
$
/
gm
\.
matches the character
.
literally (case sensitive)
Negative Lookahead
(?!
html
?
)
Assert that the Regex below does not match
htm
matches the characters
htm
literally (case sensitive)
l
?
matches the character
l
literally (case sensitive)
?
Quantifier
— Matches between
zero
and
one
times, as many times as possible, giving back as needed
(greedy)
1st Capturing Group
(
[
a
-
z
]
{0,3}
|
[
a
-
z
]
{0,4}
)
1st Alternative
[
a
-
z
]
{0,3}
Match a single character present in the list below
[
a
-
z
]
{0,3}
{0,3}
Quantifier
— Matches between
0
and
3
times, as many times as possible, giving back as needed
(greedy)
a-z
a single character in the range between
a
(index 97)
and
z
(index 122)
(case sensitive)
2nd Alternative
[
a
-
z
]
{0,4}
Match a single character present in the list below
[
a
-
z
]
{0,4}
{0,4}
Quantifier
— Matches between
0
and
4
times, as many times as possible, giving back as needed
(greedy)
a-z
a single character in the range between
a
(index 97)
and
z
(index 122)
(case sensitive)
$
asserts position at the end of a line
Lines are delimited by \n, \r, \u2028, \u2029 (with no special consideration for the \r\n sequence)
Global pattern flags
g modifier:
g
lobal. All matches (don't return after first match)
m modifier:
m
ulti line. Causes
^
and
$
to match the begin/end of each line (not only begin/end of string)
Match Information
Your regular expression does not match the subject string.
Quick Reference
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