2nd/10_Wiki/Topic_Programming/Topic_JavaScript/JavaScript_String_Methods.md

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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-string-methods	JavaScript String Methods	Frontend	draft	conceptual		string methods slice substring trim replace split padStart		B	0.88	2026-06-23	2026-06-23			javascript js web frontend w3schools strings string-methods immutability	https://www.w3schools.com/js/js_string_methods.asp

JavaScript String Methods

🎯 한 줄 통찰 (One-line insight)

Strings are immutable, so every string method produces a new string without altering the original — covering extraction (slice, substring, substr), character access (charAt, at, []), case, trimming, padding, and replacement. [S1]

🧠 핵심 개념 (Core concepts)

• Immutability — all string methods produce a new string without altering the original string; strings cannot be changed, only replaced. [S1]
• length — the length property returns the length of a string. [S1]
• Character extraction — four ways to get a character: at(), charAt(), charCodeAt(), and bracket notation []; codePointAt() returns a code point. [S1]
• at() allows negative indexes — introduced in ES2022, at() allows negative indexes while charAt() does not. [S1]
• Substring extraction — slice(), substring(), and substr() extract parts of a string; substr() is deprecated. [S1]
• replace() vs replaceAll() — replace() replaces only the first match and is case sensitive by default; replaceAll() (ES2021) replaces all matches. [S1]
• split() — converts a string into an array using a chosen delimiter. [S1]

🧩 추출된 패턴 (Extracted patterns)

• Extract a slice by index range — text.slice(start, end) (or substring) to pull a labeled portion. [S1]
• Normalize input — chain trim() / trimStart() / trimEnd() then case methods to clean user input. [S1]
• Pad to a fixed width — padStart(len, "0") to left-pad values such as IDs or amounts. [S1]
• Replace all occurrences — replaceAll(a, b), or replace() with a /g regex flag, since plain replace() only hits the first match. [S1]

📖 세부 내용 (Details)

Note: All string methods produce a new string without altering the original string. Strings are immutable: strings cannot be changed, only replaced. [S1]

Length [S1]

let text = "ABCDEFGHIJKLMNOPQRSTUVWXYZ";
let length = text.length;

charAt() — returns the character at a given index. [S1]

let text = "HELLO WORLD";
let char = text.charAt(0);

charCodeAt() — returns the UTF-16 code of the character at a given index. [S1]

let text = "HELLO WORLD";
let char = text.charCodeAt(0);

codePointAt() — returns the Unicode code point at a given index. [S1]

let text = "HELLO WORLD";
let code = text.codePointAt(0);

at() — introduced in ES2022; allows negative indexes while charAt() does not. [S1]

const name = "W3Schools";
let letter = name.at(2);

Property access [] — bracket notation reads a character by index. [S1]

let text = "HELLO WORLD";
let char = text[0];

concat() — joins two or more strings. [S1]

let text1 = "Hello";
let text2 = "World";
let text3 = text1.concat(" ", text2);

slice() — extracts a part of a string between start and end positions. [S1]

let text = "Apple, Banana, Kiwi";
let part = text.slice(7, 13);

substring() — similar to slice(). [S1]

let str = "Apple, Banana, Kiwi";
let part = str.substring(7, 13);

substr() — deprecated; second parameter is the length to extract. [S1]

let str = "Apple, Banana, Kiwi";
let part = str.substr(7, 6);

toUpperCase() [S1]

let text1 = "Hello World!";
let text2 = text1.toUpperCase();

toLowerCase() [S1]

let text1 = "Hello World!";
let text2 = text1.toLowerCase();

trim() — removes whitespace from both sides. [S1]

let text1 = "      Hello World!      ";
let text2 = text1.trim();

trimStart() — removes whitespace from the start. [S1]

let text1 = "     Hello World!     ";
let text2 = text1.trimStart();

trimEnd() — removes whitespace from the end. [S1]

let text1 = "     Hello World!     ";
let text2 = text1.trimEnd();

padStart() — pads from the start to a given length (ES2017). [S1]

let text = "5";
let padded = text.padStart(4,"0");

padEnd() — pads from the end to a given length (ES2017). [S1]

let text = "5";
let padded = text.padEnd(4,"0");

repeat() — returns a new string with a number of copies. [S1]

let text = "Hello world!";
let result = text.repeat(2);

replace() — the replace() method replaces only the first match. By default, the replace() method is case sensitive. [S1]

let text = "Please visit Microsoft!";
let newText = text.replace("Microsoft", "W3Schools");

replaceAll() — replaces all matches (ES2021); use a /g flag to replace all matches with regular expressions. [S1]

text = text.replaceAll("Cats","Dogs");
text = text.replaceAll("cats","dogs");

split() — converts a string into an array using a delimiter. [S1]

text.split(",")    // Split on commas
text.split(" ")    // Split on spaces
text.split("|")    // Split on pipe

Other methods listed by the page include isWellFormed() and toWellFormed(). [S1]

🛠️ 적용 사례 (Applied in summary)

The page's own snippets are the canonical applied examples — extracting substrings from "Apple, Banana, Kiwi", padding "5" to width 4, replacing "Microsoft" with "W3Schools", and splitting on delimiters. No external project/commit applications found in the source.

💻 코드 패턴 (Code patterns)

Extract a portion:

let part = text.slice(7, 13);

Pad to fixed width:

let padded = text.padStart(4,"0");

Replace every occurrence:

text = text.replaceAll("Cats","Dogs");

⚖️ 모순 및 업데이트 (Contradictions & updates)

substr() is noted as deprecated; prefer slice() or substring(). No other 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 Strings, JavaScript String Search, JavaScript String Templates, JavaScript Arrays
• 참조 맥락: Referenced whenever transforming, slicing, cleaning, or replacing text values.

📚 출처 (Sources)

• [S1] W3Schools — JavaScript String Methods — https://www.w3schools.com/js/js_string_methods.asp

📝 변경 이력 (Change history)

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