Regular Expressions 101

Positive Lookbehind(?<=\s|^)

1st Alternative\s

\sany whitespace character

2nd Alternative^

^start of string

Group 1(1[0-9]{3}|20(0[0-9]|1[0-2]))

1st Alternative1[0-9]{3}

1the literal 1 (49₁₀ / 61₈ / 31₁₆)

Character Class[0-9]{3}

{3}matches exactly 3 characters from the set below:

0-9one character from 0 (48₁₀) to 9 (57₁₀)

2nd Alternative20(0[0-9]|1[0-2])

20the literal text 20

Group 2(0[0-9]|1[0-2])

1st Alternative0[0-9]

0the literal 0 (48₁₀ / 60₈ / 30₁₆)

Character Class[0-9]

0-9one character from 0 (48₁₀) to 9 (57₁₀)

2nd Alternative1[0-2]

1the literal 1 (49₁₀ / 61₈ / 31₁₆)

Character Class[0-2]

0-2one character from 0 (48₁₀) to 2 (50₁₀)

Character Class[\\\/\-\s]

\\the literal \ (92₁₀ / 134₈ / 5C₁₆)

\/the literal / (47₁₀ / 57₈ / 2F₁₆)

\-the literal - (45₁₀ / 55₈ / 2D₁₆)

\sany whitespace character

Group 3(0[1-9]|1[0-2])

1st Alternative0[1-9]

0the literal 0 (48₁₀ / 60₈ / 30₁₆)

Character Class[1-9]

1-9one character from 1 (49₁₀) to 9 (57₁₀)

2nd Alternative1[0-2]

1the literal 1 (49₁₀ / 61₈ / 31₁₆)

Character Class[0-2]

0-2one character from 0 (48₁₀) to 2 (50₁₀)

Character Class[\\\/\-\s]

\\the literal \ (92₁₀ / 134₈ / 5C₁₆)

\/the literal / (47₁₀ / 57₈ / 2F₁₆)

\-the literal - (45₁₀ / 55₈ / 2D₁₆)

\sany whitespace character

Group 4(0[1-9]|[1-2][0-9]|30)

1st Alternative0[1-9]

0the literal 0 (48₁₀ / 60₈ / 30₁₆)

Character Class[1-9]

1-9one character from 1 (49₁₀) to 9 (57₁₀)

2nd Alternative[1-2][0-9]

Character Class[1-2]

1-2one character from 1 (49₁₀) to 2 (50₁₀)

Character Class[0-9]

0-9one character from 0 (48₁₀) to 9 (57₁₀)

3rd Alternative30

Positive Lookahead(?=[\s,;]|$)

Global pattern flags

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

No unit tests · Add a test to get started

Search reference

Regular Expression

(?<=\s|^)(1[0-9]{3}|20(0[0-9]|1[0-2]))[\\\/\-\s](0[1-9]|1[0-2])[\\\/\-\s](0[1-9]|[1-2][0-9]|30)(?=[\s,;]|$)

Unit Tests

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