Regular Expressions 101

Explanation

Pro

\ban ASCII word boundary

Positive Lookahead(?=(?:[a-z0-9]*[A-Z]){4})

Non-Capturing Group(?:[a-z0-9]*[A-Z]){4}

{4}repeats the group contents below exactly 4 times:

Character Class[a-z0-9]*

*matches any number of characters from the set below:

a-zone character from a (97₁₀) to z (122₁₀) (case sensitive)

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

Character Class[A-Z]

A-Zone character from A (65₁₀) to Z (90₁₀) (case sensitive)

Positive Lookahead(?=(?:[A-Z0-9]*[a-z]){2})

Non-Capturing Group(?:[A-Z0-9]*[a-z]){2}

{2}repeats the group contents below exactly 2 times:

Character Class[A-Z0-9]*

*matches any number of characters from the set below:

A-Zone character from A (65₁₀) to Z (90₁₀) (case sensitive)

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

Character Class[a-z]

a-zone character from a (97₁₀) to z (122₁₀) (case sensitive)

Positive Lookahead(?=[a-zA-Z]*[0-9])

Character Class[a-zA-Z]*

*matches any number of characters from the set below:

a-zone character from a (97₁₀) to z (122₁₀) (case sensitive)

A-Zone character from A (65₁₀) to Z (90₁₀) (case sensitive)

Character Class[0-9]

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

Character Class[A-Za-z0-9]{5,30}

{5,30}matches between 5 and 30 characters from the set below:

A-Zone character from A (65₁₀) to Z (90₁₀) (case sensitive)

a-zone character from a (97₁₀) to z (122₁₀) (case sensitive)

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

\ban ASCII word boundary

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

No unit tests

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25 tokens

\b(?=(?:[a-z0-9]*[A-Z]){4})(?=(?:[A-Z0-9]*[a-z]){2})(?=[a-zA-Z]*[0-9])[A-Za-z0-9]{5,30}\b

There are no unit tests.