2nd/10_Wiki/Topic_JavaScript/JavaScript_RegExp.md

id, title, category, status, verification_status, canonical_id, aliases, duplicate_of, source_trust_level, confidence_score, created_at, updated_at, review_reason, merge_history, tags, raw_sources, applied_in, github_commit

id	title	category	status	verification_status	canonical_id	aliases	duplicate_of	source_trust_level	confidence_score	created_at	updated_at	review_reason	merge_history	tags	raw_sources	applied_in	github_commit
javascript-regexp	JavaScript RegExp	Frontend	draft	conceptual		regular expressions regex RegExp object pattern matching regex flags metacharacters		B	0.88	2026-06-23	2026-06-23			javascript js web frontend w3schools regexp regex string	https://www.w3schools.com/js/js_regexp.asp

JavaScript RegExp

🎯 한 줄 통찰 (One-line insight)

A regular expression is a sequence of characters forming a search pattern (/pattern/flags), used in JavaScript for searching, replacing, and validating text through string methods and the RegExp object. [S1]

🧠 핵심 개념 (Core concepts)

• A regex is a search pattern — "A Regular Expression is a sequence of characters that forms a search pattern." [S1]
• Syntax — written as /pattern/modifier flags. [S1]
• String methods — match(regex) returns an array of results, replace(regex) returns a new string, and search(regex) returns the index of the first match. [S1]
• Flags — /g global match, /i case-insensitive, /u Unicode support (new 2015). [S1]
• Metacharacters — \d digits, \w word characters, \s spaces. [S1]
• Quantifiers — x+, x*, x? control how many occurrences match. [S1]
• Assertions — ^, $, \b, lookahead (?=...), lookbehind (?<=...). [S1]
• Character classes — [a], [abc], [a-z], [0-9] match sets/ranges of characters. [S1]

🧩 추출된 패턴 (Extracted patterns)

• String method + regex literal — call text.match(/.../), text.search(/.../), or text.replace(/.../, ...) with an inline regex. [S1]
• Flag-driven behavior — append g to find all matches and i to ignore case. [S1]
• pattern.test(text) for boolean validation — use anchored patterns (^, $) with .test() to validate where a substring sits. [S1]

📖 세부 내용 (Details)

Regular Expressions Overview "A Regular Expression is a sequence of characters that forms a search pattern." Regular expressions in JavaScript are handled through the RegExp object and are used for text searching, replacing, and validation. [S1]

Syntax — /pattern/modifier flags. [S1]

Using String Methods — three primary string methods work with regex: match(regex) returns an array; replace(regex) returns a new string; search(regex) returns the index of the first match. [S1]

Case-insensitive search: [S1]

let text = "Visit W3Schools";
let n = text.search(/w3schools/i);

Using match(): [S1]

let text = "Visit W3Schools";
let n = text.match(/W3schools/);

Using replace(): [S1]

let text = "Visit Microsoft!";
let result = text.replace(/Microsoft/i, "W3Schools");

Using search(): [S1]

let text = "Visit W3Schools";
let n = text.search(/W3Schools/);

Alternation (OR): [S1]

let text = "Black, white, red, green, blue, yellow.";
let result = text.match(/red|green|blue/g);

Regex Flags [S1]

Flag	Description
/g	Performs a global match (find all)
/i	Performs case-insensitive matching
/u	Enables Unicode support (new 2015)

Global flag: [S1]

let text = "Is this all there is?";
const pattern = /is/g;
let result = text.match(pattern);

Case-insensitive flag: [S1]

let text = "Visit W3Schools";
const pattern = /w3schools/i;
let result = text.match(pattern);

Metacharacters — common metacharacters include \d (digits), \w (words), and \s (spaces). [S1]

Digits metacharacter: [S1]

let text = "Give 100%!";
const pattern = /\d/g;
let result = text.match(pattern);

Word characters: [S1]

let text = "Give 100%!";
const pattern = /\w/g;
let result = text.match(pattern);

Quantifiers [S1]

Quantifier	Description
x+	Matches any string with at least one occurrence of x
x*	Matches any string with zero or more occurrences of x
x?	Matches any string with zero or one occurrence of x

Question-mark quantifier: [S1]

let text = "1, 100 or 1000?";
const pattern = /10?/g;
let result = text.match(pattern);

Assertions — string boundaries and lookarounds: [S1]

Syntax	Name	Description
^	String boundary	Matches the beginning of a string
$	String boundary	Matches the end of a string
\b	Word boundary	Matches the beginning or end of a word
(?=...)	Lookahead	Matches the subsequent string
(?<=...)	Lookbehind	Matches the previous string

Caret (beginning) — true: [S1]

const pattern = /^W3Schools/;
let text = "W3Schools Tutorial";
let result = pattern.test(text); // true

Caret (beginning) — false: [S1]

const pattern = /^W3Schools/;
let text = "Hello W3Schools";
let result = pattern.test(text); // false

Dollar (end) — true: [S1]

const pattern = /W3Schools$/;
let text = "Hello W3Schools";
let result = pattern.test(text); // true

Dollar (end) — false: [S1]

const pattern = /W3Schools$/;
let text = "W3Schools tutorial";
let result = pattern.test(text); // false

Character Classes [S1]

Class	Description
[a]	Matches the character between the brackets
[abc]	Matches all characters between the brackets
[a-z]	Matches all characters in the range from a to z
[0-9]	Matches all characters in the range from 0 to 9

Character class [0-9]: [S1]

let text = "More than 1000 times";
const pattern = /[0-9]/g;
let result = text.match(pattern);

The page concludes with links to related topics including RegExp flags, character classes, meta characters, assertions, groups, quantifiers, patterns, objects, and methods. [S1]

🛠️ 적용 사례 (Applied in summary)

The page's snippets are the canonical applied examples — case-insensitive search, match/replace, alternation, the g/i flags, the \d/\w metacharacters, the ? quantifier, anchored .test() validation, and the [0-9] character class. No external project/commit applications found in the source.

💻 코드 패턴 (Code patterns)

Search, match, and replace with regex literals (language: JavaScript):

text.search(/w3schools/i);           // index of first match, case-insensitive
text.match(/red|green|blue/g);       // all alternation matches
text.replace(/Microsoft/i, "W3Schools"); // returns new string

Validate position with anchors and .test():

/^W3Schools/.test("W3Schools Tutorial"); // true  (starts with)
/W3Schools$/.test("Hello W3Schools");    // true  (ends with)

⚖️ 모순 및 업데이트 (Contradictions & updates)

No contradictions found in the source.

✅ 검증 상태 및 신뢰도

• 상태: draft
• 검증 단계: conceptual (실제 적용 사례 발견 시 applied/validated로 승격 가능)
• 출처 신뢰도: B (W3Schools — widely used educational reference, not a primary standards body)
• 신뢰 점수: 0.88
• 중복 검사 결과: 신규 생성 (New discovery)

🔗 지식 그래프 (Knowledge Graph)

• 상위/루트: JavaScript Tutorial
• 관련 개념: JavaScript String Methods, JavaScript String Search, JavaScript Type Conversion, JavaScript Form Validation
• 참조 맥락: The pattern-matching toolkit used by string methods for searching, replacing, and validating text input.

📚 출처 (Sources)

• [S1] W3Schools — JavaScript RegExp — https://www.w3schools.com/js/js_regexp.asp

📝 변경 이력 (Change history)

• 2026-06-23: Initial draft synthesized from the W3Schools "JavaScript RegExp" page (Astra wiki-curation, P-Reinforce v3.1 format).