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正規表達式元字元・標誌・類別的互動式參考

all
meta
quantifier
class
anchor
group
lookaround
flag

38 entries

meta
.

Any single character except newline

a.c → 'abc'

meta
\d

Digit (0-9)

\d+ → '123'

meta
\D

Non-digit

\D+ → 'abc'

meta
\w

Word char [A-Za-z0-9_]

\w+ → 'foo_1'

meta
\W

Non-word char

\W → '!'

meta
\s

Whitespace (space, tab, newline)

a\sb → 'a b'

meta
\S

Non-whitespace

\S+ → 'foo'

meta
\b

Word boundary

\bcat\b → 'cat'

meta
\B

Non-word boundary

\Bcat → 'concat'

quantifier
*

0 or more (greedy)

a* → '', 'aaa'

quantifier
+

1 or more (greedy)

a+ → 'aaa'

quantifier
?

0 or 1 (optional)

colou?r → 'color', 'colour'

quantifier
{n}

Exactly n times

\d{4} → '2025'

quantifier
{n,}

n or more times

\d{2,} → '12', '123'

quantifier
{n,m}

Between n and m times

\d{2,4} → '12', '1234'

quantifier
*?

0 or more (lazy)

<.*?> → '<a>', '<b>'

quantifier
+?

1 or more (lazy)

.+? → minimal match

class
[abc]

Any one of a, b, c

[aeiou] → vowels

class
[^abc]

None of a, b, c

[^0-9] → non-digit

class
[a-z]

Range a to z

[A-Za-z] → letters

class
[\d\s]

Combined classes

[\d\.] → digit or dot

anchor
^

Start of string (or line with /m)

^foo → starts with foo

anchor
$

End of string (or line with /m)

bar$ → ends with bar

group
(abc)

Capturing group

(\d+)-(\w+) → captures both

group
(?:abc)

Non-capturing group

(?:foo|bar)+

group
(?<name>abc)

Named capture group

(?<year>\d{4})

group
a|b

Alternation (or)

cat|dog → 'cat' or 'dog'

group
\1

Backreference to group 1

(\w)\1 → 'oo' in 'book'

lookaround
(?=abc)

Positive lookahead

\d(?=px) → '12' in '12px'

lookaround
(?!abc)

Negative lookahead

\d(?!px) → digit not followed by px

lookaround
(?<=abc)

Positive lookbehind

(?<=\$)\d+ → '100' in '$100'

lookaround
(?<!abc)

Negative lookbehind

(?<!\$)\d+ → digit not after $

flag
g

Global — all matches

/foo/g

flag
i

Case-insensitive

/FOO/i → matches 'foo'

flag
m

Multiline — ^/$ per line

/^line/m

flag
s

Dotall — . matches newline

/a.b/s

flag
u

Unicode mode

/\u{1F600}/u

flag
y

Sticky — match from lastIndex

/foo/y

使用方法

  1. Type a keyword such as 'lookahead', 'quantifier', or '\d' into the search box to filter entries。
  2. Click a category badge to narrow results to Anchors, Groups, Quantifiers, Classes, or Lookarounds。
  3. Click any card to copy its syntax to the clipboard。
  4. Share your filtered view with the copy-link button at the bottom。

範例

  • Searching 'lookahead' narrows the list to (?=...) and (?!...) entries with descriptions and examples。
  • Clicking the Quantifiers badge shows entries like +, *, ?, {n,m} — each card shows the syntax, description, and a short example string。

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