Regular Expressions 101

^start of line

Comment: anchors the expression to the beginning

Positive Lookahead(?=[^a-z]*[a-z])

Negated Character Class[^a-z]*

*matches any number of characters outside the set below:

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

Character Class[a-z]

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

Comment: not lowercase, followed by lowercase

Positive Lookahead(?=[^A-Z]*[A-Z])

Negated Character Class[^A-Z]*

*matches any number of characters outside the set below:

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

Character Class[A-Z]

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

Comment: not UPPERCASE, followed by UPPERCASE

Positive Lookahead(?=\D*\d)

\D*any character that is not a Unicode decimal digit, repeated any number of times

\da Unicode decimal digit

Comment: not a digit, followed by a digit

.{8,}any Unicode character (except for line terminators), repeated at least 8 times

Comment: at least 8 characters long

$end of line

Comment: anchor the expression to the end

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

x modifier: extended. Ignores unescaped whitespace and comments outside character classes

No unit tests · Add a test to get started

25 tokens

Regular Expression

    ^                    # anchors the expression to the beginning
        (?=[^a-z]*[a-z]) # not lowercase, followed by lowercase
        (?=[^A-Z]*[A-Z]) # not UPPERCASE, followed by UPPERCASE
        (?=\D*\d)        # not a digit, followed by a digit
        .{8,}            # at least 8 characters long
    $                    # anchor the expression to the end

Unit Tests

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