2nd/10_Wiki/Topic_JavaScript/JavaScript_Objects.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-objects	JavaScript Objects	Frontend	draft	conceptual		JS objects object literal object definitions new Object key value pairs objects are mutable primitives		B	0.86	2026-06-23	2026-06-23			javascript js web frontend w3schools objects object-literal primitives	https://www.w3schools.com/js/js_objects.asp https://www.w3schools.com/js/js_object_definition.asp

JavaScript Objects

🎯 한 줄 통찰 (One-line insight)

Objects are variables that can store both values and functions, and in JavaScript almost everything except primitives is an object — addressed by reference, not by value. [S1][S2]

🧠 핵심 개념 (Core concepts)

• Objects store values and functions — they are one of the most important concepts in JavaScript. [S1]
• Key:value pairs — an object literal is a list of property key:value pairs inside curly braces { }. [S2]
• Many ways to define — object literal, the new keyword, an object constructor, Object.assign(), Object.create(), and Object.fromEntries(). [S2]
• Objects are king — in JavaScript almost everything is an object; all JavaScript values except primitives are objects. [S2]
• Objects are mutable and passed by reference — they are addressed by reference, not by value, so a "copy" actually shares the same memory. [S2]
• Primitives are immutable — the seven primitive types hold a single value that cannot be changed. [S2]

🧩 추출된 패턴 (Extracted patterns)

• Prefer the object literal — for readability, simplicity, and execution speed, use the object literal over new Object(). [S2]
• Reference-aliasing caution — const x = person; does not copy; x is person, so changing x.age changes person.age. [S2]
• Build objects from data — Object.fromEntries() constructs an object from iterable key/value pairs; Object.assign() merges sources into a target. [S2]

📖 세부 내용 (Details)

What JavaScript objects are Objects are variables that can store both values and functions, and they are one of the most important concepts in JavaScript. The learning path covers object basics, properties (which can be changed, added, and deleted), methods (functions stored as property values), the this keyword (which refers to the calling object), display techniques (loops and JSON.stringify()), and constructors (for creating multiple objects of the same type). [S1]

Using an Object Literal An object literal is a list of property key:value pairs inside curly braces { }. [S2]

{firstName:"John", lastName:"Doe", age:50, eyeColor:"blue"};

// Create an Object
const person = {
  firstName: "John",
  lastName: "Doe",
  age: 50,
  eyeColor: "blue"
};

Note: there is no need to use new Object(). For readability, simplicity, and execution speed, use the object literal method. Objects written as name/value pairs are similar to associative arrays in PHP, dictionaries in Python, hash tables in C, hash maps in Java, and hashes in Ruby and Perl. [S2]

Using the new Keyword [S2]

// Create an Object
const person = new Object({
  firstName: "John",
  lastName: "Doe",
  age: 50,
  eyeColor: "blue"
});

The examples above do exactly the same. [S2]

Object.create() The Object.create() method creates an object from an existing object. [S2]

// Create an Object:
const person = {
  firstName: "John",
  lastName: "Doe"
};

// Create new Object
const man = Object.create(person);
man.firstName = "Peter";

Object.fromEntries() ES2019 added the fromEntries() method, which creates an object from iterable key/value pairs. [S2]

const fruits = [
["apples", 300],
["pears", 900],
["bananas", 500]
];

const myObj = Object.fromEntries(fruits);

fromEntries() is an ECMAScript 2019 feature, supported in all modern browsers since January 2020. [S2]

Browser	Version	Release Date
Chrome	66	Apr 2018
Edge	79	Jan 2020
Firefox	61	Jun 2018
Safari	12	Sep 2018
Opera	50	May 2018

Object.assign() The Object.assign() method copies properties from one or more source objects to a target object. [S2]

// Create Target Object
const person1 = {
  firstName: "John",
  lastName: "Doe",
  age: 50,
  eyeColor: "blue"
};

// Create Source Object
const person2 = {firstName: "Anne",lastName: "Smith"};

// Assign Source to Target
Object.assign(person1, person2);

In JavaScript, Objects are King "If you understand objects, you understand JavaScript." In JavaScript, almost everything is an object: objects are objects, maths are objects, functions are objects, dates are objects, arrays are objects, maps are objects, and sets are objects. All JavaScript values, except primitives, are objects. [S2]

JavaScript Primitives A primitive data type can only store a single primitive value. There are seven primitive types: [S2]

Type	Example Value
string	"Hello"
number	3.14
boolean	true
bigint	12345678901234n
null	null
undefined	undefined
symbol	symbol

Primitive values are immutable (they are hardcoded and cannot be changed). If x = 3.14, you can change the value of x, but you cannot change the value of 3.14. [S2]

JavaScript Objects are Mutable Objects are mutable: they are addressed by reference, not by value. If person is an object, const x = person; will not create a copy of person. The object x is not a copy of person — x is person; they share the same memory address, and any change to x also changes person: [S2]

//Create an Object
const person = {
  firstName:"John",
  lastName:"Doe",
  age:50, eyeColor:"blue"
}

// Try to create a copy
const x = person;

// This will change age in person:
x.age = 10;

⚖️ 비교 및 선택 기준 (Comparison & decision criteria)

Definition method	When to use	Note
Object literal { }	Default choice	Best readability, simplicity, execution speed [S2]
new Object()	Equivalent to literal	Does exactly the same; literal preferred [S2]
Object.create()	Create from an existing object	Inherits from the source object [S2]
Object.assign()	Merge sources into a target	Copies properties from source(s) [S2]
Object.fromEntries()	Build from key/value pairs	ES2019 feature [S2]

🛠️ 적용 사례 (Applied in summary)

The page's own snippets are the canonical applied examples — the person object literal, the new Object() equivalent, Object.create()/Object.assign()/Object.fromEntries(), and the reference-aliasing demonstration. No external project/commit applications found in the source.

💻 코드 패턴 (Code patterns)

Preferred object literal:

const person = {
  firstName: "John",
  lastName: "Doe",
  age: 50,
  eyeColor: "blue"
};

Reference aliasing (not a copy):

const x = person;
x.age = 10; // also changes person.age

Build an object from key/value pairs:

const myObj = Object.fromEntries(fruits);

⚖️ 모순 및 업데이트 (Contradictions & updates)

No contradictions found in the source. Version notes: Object.fromEntries() is an ECMAScript 2019 feature supported in all modern browsers since January 2020. [S2]

✅ 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: 0.86
• 중복 검사 결과: 신규 생성 (New discovery). Note: the js_objects.asp page is an overview/index; code detail is grounded in the linked "Object Definitions" lesson [S2].

🔗 지식 그래프 (Knowledge Graph)

• 상위/루트: JavaScript Tutorial
• 관련 개념: JavaScript Object Properties, JavaScript Object Methods, JavaScript Object this, JavaScript Object Display
• 참조 맥락: The foundation for all object-related topics — properties, methods, this, and display.

📚 출처 (Sources)

• [S1] W3Schools — JavaScript Objects — https://www.w3schools.com/js/js_objects.asp
• [S2] W3Schools — JavaScript Object Definitions — https://www.w3schools.com/js/js_object_definition.asp

📝 변경 이력 (Change history)

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