Master Regular Expressions from scratch - All languages

Master regular expressions by learning literal character matching within strings of letters, numbers, symbols, and punctuation, and explore how case-insensitive matching changes results using the I flag.

Explore the global flag in regular expressions, learning how turning global on matches all occurrences from left to right, while off matches only the leftmost earliest occurrence.

Master regex metacharacters, including backslash, dot, plus, braces, dollar sign, question mark, bar, exclamation, and equals; learn context-driven meanings and how single-line mode affects newline handling.

Learners master escaping metacharacters in regular expressions by using backslashes to denote literals, including dots and backslashes themselves, and recognize the role of forward slashes as delimiters.

Master regular expressions from scratch using character sets and character classes, exploring opening and closing brackets, matching any one of several characters, and the role of wildcards in precise patterning.

Master character ranges in regular expressions by using hyphen notation inside a character class to match lowercase and uppercase letters, digits (0-9), and alphanumeric sets without spaces.

Master negative character sets by learning how negated character classes match any character not in a set, with examples like [^0-9] that exclude digits and validate single-character matches.

Explore metacharacters inside character sets, learn which characters must be escaped, how hyphens and brackets behave in character classes, and how the regex engine interprets these rules.

Master shorthand character sets in regular expressions by using backslash escapes for word, digit, and whitespace classes, exploring their behavior inside character classes and common pitfalls.

Learn posix bracket expressions inside character classes, using shorthand sets like [:alpha:] and ranges like [A-Z] and [0-9], with language support noted for Perl, Ruby, and Unix.

Learn how repetition metacharacters regulate preceding characters with zero or more, one or more, and zero or one, using bananas and character classes as examples.

Explore quantified repetition expressions in regular expressions, using braces to define minimum and maximum repeats of the preceding item, including finite and infinite repeats and two-letter matches.

Explore how regex engines use greedy and lazy quantifiers, backtracking, and repetition rules to find matches, with examples of longest versus minimal matches.

Explore grouping metacharacters in regular expressions by using parentheses to delimit groups, apply repetition to the whole group, and capture submatches for easier reading and targeted replacements.

Explore the alternation metacharacter in regular expressions, using the vertical bar to match left or right expressions, with grouping for multiple options and examples of misspellings, and leftmost expression precedence.

Explore repeating and nesting alternations in regular expressions, focusing on the character class. See how grouped alternations with four repetitions match x x, y y, z z in any order.

Explore start and end anchors in regular expressions, using caret and dollar signs to mark string or line boundaries and reference positions rather than matching characters.

Learn how line breaks influence regular expressions and how multiline mode affects start and end anchors ^ and $. See default single line mode and how line boundaries differ.

Explore word boundaries in regular expressions, using \b and \B to distinguish word and non-word positions, with examples like learning is my passion and underscore as a word character.

Master backreferences by using capturing groups to refer to matched data in a regex and reuse it in replacements, with syntax like \1 and $1 across engines.

Explore how backreferences interact with optional groups in regular expressions, including when groups match or become empty, and note differences between JavaScript/ECMAScript and other engines.

Discover non-capturing groups in regular expressions with the (?:) syntax, and learn how avoiding captures can speed up matching while exploring back references and octal escapes.

Master positive lookahead assertions in regex, a zero-width check that verifies upcoming patterns without consuming characters, enabling efficient matching through group expressions and backtracking control.

Master negative lookahead assertions, the opposite of positive lookahead, using (?!...) to ensure text does not follow; the engine continues parsing, shown by an example of 'work' vs 'worked'.

Explore look behind assertions in regular expressions, including positive and negative forms, yielding zero-width matches. Compare syntax rules, fixed-length requirements, and language support across Java, .NET, Ruby, and JavaScript.

Explore Unicode and multibyte characters, encoding, and hex code points, using escapes like \uXXXX in regular expressions. Learn properties and cross-language regex challenges, practicing emails and IP address patterns.

Craft regular expressions that match names using start and end anchors and multiline mode, capture first and last names with groups, handle apostrophes and hyphens, and make middle names optional.

Learn to write country-specific regular expressions for postal codes, covering the United States, Canada, and Spain, with anchors, optional groups, and non-capturing groups to validate formats.

Write a regular expression to match urls, covering protocol, domain and subdomain, path segments, query parameters, and optional file endings, using character classes and repetition.

Learn to write regular expressions that match credit card numbers for American Express, Visa, MasterCard, and Discover, including patterns with or without delimiters and type-detecting prefixes.

Learn to write a regular expression that matches email addresses, using anchors, a negated first-letter class, local and domain parts, and a domain extension pattern.

Develop a regex to match HTML tags, including opening and closing tags with attributes and self-closing variants, using backreferences, non-capturing groups, and flexible attribute handling.

Master a regular expression that matches IPv4 addresses by validating four octets (0-255) separated by dots, using anchors and grouping to ensure correct patterns.

Write a regular expression to validate passwords from 6 to 30 characters with no spaces, using lookahead assertions and anchors ^ and $ to require uppercase, lowercase, numbers, and symbols.