2nd/10_Wiki/Topic_JavaScript/JavaScript_Number_Methods.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-number-methods	JavaScript Number Methods	Frontend	draft	conceptual		number methods toFixed toPrecision Number() parseInt parseFloat		B	0.89	2026-06-23	2026-06-23			javascript js web frontend w3schools numbers number-methods parsing	https://www.w3schools.com/js/js_number_methods.asp

JavaScript Number Methods

🎯 한 줄 통찰 (One-line insight)

Basic number methods (toString, toExponential, toFixed, toPrecision, valueOf) work on any number, while static Number.* methods (isInteger, isFinite, isNaN, isSafeInteger, parseInt, parseFloat) can only be used on Number itself. [S1]

🧠 핵심 개념 (Core concepts)

• Basic methods work on any number — toString(), toExponential(), toFixed(), toPrecision(), valueOf(). [S1]
• Static methods only on Number — Number.isFinite(), Number.isInteger(), Number.isNaN(), Number.isSafeInteger(), Number.parseInt(), Number.parseFloat(). [S1]
• toString() — returns a number as a string; accepts a radix. [S1]
• toFixed() — returns a string with a specified number of decimals; perfect for working with money. [S1]
• toPrecision() — returns a string with a number written to a specified length. [S1]
• Conversion functions — Number(), parseInt(), parseFloat() convert variables to numbers; NaN is returned when conversion fails. [S1]
• Methods cannot be used on variables for statics — Number.isInteger() etc. must be called on Number; calling on a variable throws a TypeError. [S1]
• Safe integers — range is -(2⁵³ - 1) to +(2⁵³ - 1); 9007199254740991 is safe, 9007199254740992 is not. [S1]

🧩 추출된 패턴 (Extracted patterns)

• Format money — value.toFixed(2) to render two decimal places. [S1]
• Parse leading number from text — parseInt("10 years") / parseFloat("10.33") extract a number from the front of a string. [S1]
• Validate before use — Number.isInteger() / Number.isSafeInteger() / Number.isNaN() to check values. [S1]

📖 세부 내용 (Details)

Basic Methods can be used on any number: toString(), toExponential(), toFixed(), toPrecision(), valueOf(). Static Methods can only be used on Number: Number.isFinite(), Number.isInteger(), Number.isNaN(), Number.isSafeInteger(), Number.parseInt(), Number.parseFloat(). [S1]

toString() — returns a number as a string; can take a radix. [S1]

let x = 123;
x.toString();
(123).toString();
(100 + 23).toString();

let x = 123;
let text = x.toString(2);

toExponential() — returns a string with a number rounded and written using exponential notation. [S1]

let x = 9.656;
x.toExponential(2);
x.toExponential(4);
x.toExponential(6);

toFixed() — returns a string with the number written with a specified number of decimals; perfect for working with money. [S1]

let x = 9.656;
x.toFixed(0);
x.toFixed(2);
x.toFixed(4);
x.toFixed(6);

toPrecision() — returns a string with a number written with a specified length. [S1]

let x = 9.656;
x.toPrecision();
x.toPrecision(2);
x.toPrecision(4);
x.toPrecision(6);

valueOf() — returns a number as a number; used internally in JavaScript to convert Number objects to primitive values. [S1]

let x = 123;
x.valueOf();
(123).valueOf();
(100 + 23).valueOf();

Converting Variables to Numbers — three methods are available: [S1]

Method	Description
Number()	Converts argument to number
parseFloat()	Parses argument, returns floating point
parseInt()	Parses argument, returns whole number

Number() — converts its argument to a number. [S1]

Number(true);
Number(false);
Number("10");
Number("  10");
Number("10  ");
Number(" 10  ");
Number("10.33");
Number("10,33");
Number("10 33");
Number("John");

Number() Used on Dates — converts a date to milliseconds. [S1]

Number(new Date("1970-01-01"))

Number(new Date("1970-01-02"))

Number(new Date("2017-09-30"))

parseInt() — parses and returns a whole number. [S1]

parseInt("-10");
parseInt("-10.33");
parseInt("10");
parseInt("10.33");
parseInt("10 20 30");
parseInt("10 years");
parseInt("years 10");

parseFloat() — parses and returns a floating point number. [S1]

parseFloat("10");
parseFloat("10.33");
parseFloat("10 20 30");
parseFloat("10 years");
parseFloat("years 10");

Number Object Methods (static): [S1]

Method	Description
Number.isInteger()	Returns true if argument is integer
Number.isNaN()	Returns true if argument is NaN
Number.isFinite()	Returns true if not Infinity or NaN
Number.isSafeInteger()	Returns true if safe integer
Number.parseFloat()	Converts string to number
Number.parseInt()	Converts string to whole number

Number methods can only be accessed like Number.isInteger(); calling them on a variable produces a TypeError ("X.isInteger is not a function"). Number.isNaN() is the preferred way to check for equality with NaN. [S1]

Number.isInteger() [S1]

Number.isInteger(10);
Number.isInteger(10.5);

Number.isFinite() [S1]

Number.isFinite(123);

Number.isNaN() [S1]

Number.isNaN(123);

Number.isSafeInteger() — safe integer range is -(2⁵³ - 1) to +(2⁵³ - 1). [S1]

Number.isSafeInteger(10);
Number.isSafeInteger(12345678901234567890);

Number.parseFloat() [S1]

Number.parseFloat("10");
Number.parseFloat("10.33");
Number.parseFloat("10 20 30");
Number.parseFloat("10 years");
Number.parseFloat("years 10");

Number.parseInt() [S1]

Number.parseInt("-10");
Number.parseInt("-10.33");
Number.parseInt("10");
Number.parseInt("10.33");
Number.parseInt("10 20 30");
Number.parseInt("10 years");
Number.parseInt("years 10");

🛠️ 적용 사례 (Applied in summary)

The page's own snippets are the canonical applied examples — formatting 9.656 with toFixed/toPrecision/toExponential, converting strings and dates with Number(), parsing with parseInt/parseFloat, and validating with the static Number.* methods. No external project/commit applications found in the source.

💻 코드 패턴 (Code patterns)

Format for money:

let x = 9.656;
x.toFixed(2);

Parse a number from text:

parseInt("10 years");
parseFloat("10.33");

Validate a value:

Number.isInteger(10);
Number.isSafeInteger(9007199254740991);

⚖️ 비교 및 선택 기준 (Comparison & decision criteria)

• Number() vs parseInt() vs parseFloat() — Number() converts the whole argument (returns NaN if it is not fully numeric, e.g. "10 33"); parseInt() returns a whole number from the leading numeric portion; parseFloat() returns a floating point from the leading numeric portion. [S1]
• Basic vs static methods — basic methods (toFixed, etc.) are called on a number value; static methods (Number.isInteger, etc.) must be called on Number itself or they throw a TypeError. [S1]
• Number.isNaN() is preferred for checking equality with NaN. [S1]

⚖️ 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: 0.89
• 중복 검사 결과: 신규 생성 (New discovery)

🔗 지식 그래프 (Knowledge Graph)

• 상위/루트: JavaScript Tutorial
• 관련 개념: JavaScript Numbers, JavaScript Number Properties, JavaScript Data Types, JavaScript Operators
• 참조 맥락: Referenced whenever formatting numbers for display or converting strings/dates into numeric values.

📚 출처 (Sources)

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

📝 변경 이력 (Change history)

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