progmamun / regEx

A regular expression is a sequence of characters that specifies a search pattern in text. Usually such patterns are used by string-searching algorithms for "find" or "find and replace" operations on strings, or for input validation.

my notes about: Regular expression

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Basics

• / expression / flags, /[A-Z]+/g basic format
• / hello\?\*\\/ escape special characters with backslashes
• () group with parentheses
• | logical OR

Character Classes

• \w word \d digit \s whitespace, tabs, line breaks
• \w NOT word \D NOT digit \S NOT whitespace
• \t tabs, \n line breaks
• . any character (except newline)

Brackets

• [xyz] match any x, y, z
• [J-Z] match any capital letters between J & Z.
• [^xyz] NOT x, y, z

Quantification

• bob|alice match bob or alice
• z? zero or one occurrences
• z* zero or multiple occurrences
• z+ one or multiple occurrences
• z{n} n occurrences
• z{min, max} min/ max occurrences

Anchors

• hello world exact match
• ^hello start of the strings
• world$ end of the string