ورقة مرجع التعابير النمطية: البناء والأعلام والأنماط
Quick Answer
. = أي حرف، * = صفر+، + = واحد+، ? = اختياري، [] = فئة، () = مجموعة، ^ = بداية، $ = نهاية. استخدم أداة اختبار التعابير النمطية المجانية للمطابقة في الوقت الفعلي في متصفحك.
Introduction
التعابير النمطية تستخدم أحرف خاصة للأنماط: . (أي حرف)، * (صفر أو أكثر)، + (واحد أو أكثر)، ? (اختياري)، [] (فئة أحرف)، () (مجموعة)، | (أو). المراسي: ^ (بداية)، $ (نهاية). الأعلام: g (عالمي)، i (غير حساس)، m (متعدد الأسطر).
Step by Step
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Character classes —match a set of characters
[abc] matches a, b, or c. [^abc] matches anything except a, b, c. [a-z] matches any lowercase letter. Predefined classes: \d = [0-9], \D = non-digit, \w = [A-Za-z0-9_], \W = non-word, \s = whitespace, \S = non-whitespace, . = any character except newline (use s flag to include newline).
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Quantifiers —how many times to repeat
* = 0 or more. + = 1 or more. ? = 0 or 1. {n} = exactly n. {n,} = at least n. {n,m} = between n and m. Add ? for lazy matching (e.g. *? matches as few as possible). Greedy is the default and can cause catastrophic backtracking on nested patterns.
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Anchors and boundaries —where to match
^ matches the start of the string (or line with m flag). $ matches the end. \b matches a word boundary (between \w and \W). \B matches a non-word-boundary. Anchors are zero-width —they test position without consuming characters.
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Groups and alternation
(abc) is a capturing group; use $1, $2 in replacements. (?:abc) is a non-capturing group. (?=abc) is a lookahead (asserts what follows). (?!abc) is a negative lookahead. (?<=abc) is a lookbehind (ES2018+). a|b is alternation (a or b).
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Flags —change matching behavior
g = global (find all matches, not just the first). i = case-insensitive. m = multiline (^ and $ match line boundaries). s = dotAll (. matches newline). u = unicode (treat the pattern as Unicode code points; needed for emoji and astral characters). y = sticky (match at lastIndex only).
Examples
Match an email address (practical, RFC 5322 simplified)
Input: Pattern: /^[^\s@]+@[^\s@]+\.[^\s@]+$/
Output: Matches 'user@example.com' and 'a.b@sub.domain.co' but not 'plainaddress' or '@no-user.com'
Extract all hex color codes from CSS
Input: Pattern: /#[0-9a-fA-F]{3,8}\b/g
Output: In 'color: #fff; background: #1a2b3c4d' finds ['#fff', '#1a2b3c4d']
Validate an ISO 8601 date (YYYY-MM-DD)
Input: Pattern: /^\d{4}-(0[1-9]|1[0-2])-(0[1-9]|[12]\d|3[01])$/
Output: Matches '2026-08-28' but rejects '2026-13-01' and '2026-02-31'
Replace digits with # using a capturing group
Input: 'Order 42 shipped' replaced by /(\d+)/g →'#$1'
Output: 'Order #42 shipped'
Common Problems
- Greedy quantifiers matching too much: '<.*>' on '<a><b>' matches the whole string '<a><b>' instead of '<a>'. Use '<.*?>' (lazy) to match '<a>' first.
- Catastrophic backtracking: nested quantifiers like (a+)+b on input 'aaaaaaaaaaaaaaaa!' can take exponential time. Rewrite the pattern or use atomic groups / possessive quantifiers where supported.
- Forgetting the u flag for Unicode: /^.$/ matches a single code unit, so emoji like '😀' (two code units) fails without the u flag. Always add u when matching astral characters.
- Confusing \b (word boundary) with \s (whitespace): \b matches between a word and non-word character, so it works at start/end of string too. \s only matches actual whitespace characters.
Tips
- Always test regex against both matching and non-matching samples in our Regex Tester before embedding it in production code —edge cases are easy to miss.
- Prefer character classes [a-z] over alternation (a|b|...|z) for single characters —classes are faster and clearer.
- Use non-capturing groups (?:...) when you do not need the captured value —capturing has a small performance cost and clutters the result array.
- Compile regex once with new RegExp() or a literal at module scope, not inside a hot loop —recompiling the same pattern on every iteration wastes CPU.