基本クラス: \d \w \s

Beyond literal characters, regex give you predefined classes: shortcuts for "any digit", "any word character", "any whitespace". They are the first step toward truly useful patterns.

Each one matches a single character. To match "one or more characters" you need quantifiers (+, in module 2), but we will use + right away because "find me all the numbers" is too useful to wait for.

Pattern: \d+
Sample:  Ho 3 mele, 12 pere e 100 prugne.
            ^      ^^      ^^^

\d+ means one or more consecutive digits: it matches 3, 12 and 100 as three separate matches (with the g flag).

\w: word characters

\w is equivalent to [A-Za-z0-9_] (ASCII letters, digits, underscore). It does NOT include accents, Greek letters or emoji: for those you need Unicode property escapes (\p{L}, module 5).

Deep dive into basic classes and negations

Predefined classes \\d, \\w, \\s speed up coding. Uppercase versions (\\D, \\W, \\S) negate the set. For instance, \\S+ captures any block of text devoid of spaces (like whole words including punctuation). The engine handles \\s by matching not only the standard space, but also tabs (\\t) and newline characters (\\n or \\r).

Try it

Review exercise

Additional challenge