Basics
Objects
Key-Value Pairs
💡 Object ek ID card jaisa hai — har field ka naam (key) aur uski value (jaise "name: Aarav", "age: 20"). Related data ko ek saath group karne ka natural tareeka.
Object {} key-value pairs store karta hai — Python ke dictionary, Java ke HashMap jaisa concept, lekin JavaScript mein ye ek core, first-class data structure hai. Access karne ke do tareeke: dot notation (obj.key) aur bracket notation (obj["key"]).
const person = {
name: "Aarav",
age: 20,
isStudent: true
};
console.log(person.name); // dot notation — "Aarav"
console.log(person["age"]); // bracket notation — 20
person.city = "Mumbai"; // naya property add karo
person.age = 21; // existing update karo
for (const key in person) {
console.log(key + ": " + person[key]);
}
const { name, age } = person; // destructuring (preview — ES6+ topic mein detail)🗂️
Object ek ID card jaisa hai — har field ka naam (key) aur uski value (jaise "name: Aarav", "age: 20"). Related data ko ek saath group karne ka natural tareeka.
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⚡ झट से Recap
- {} se object banta hai — key-value pairs
- Dot notation (obj.key) ya bracket notation (obj["key"])
- Bracket notation zaroori hai dynamic keys ke liye
इस page में (2 subtopics)
Objects ke andar objects — related, hierarchical data represent karne ke liye, jaise ek user object jiske andar ek address object ho.
const user = {
name: "Aarav",
address: {
city: "Mumbai",
pincode: "400001"
}
};
console.log(user.address.city); // "Mumbai" — chained dot accessTip: Deeply nested objects access karte waqt optional chaining (?.) use karo safety ke liye — user.address?.city agar address missing ho to crash nahi karega.
Objects ke andar functions bhi ho sakte hain (methods kehlate hain) — this keyword se object ke apne properties access kar sakte hain (this ka detail Advanced JavaScript category mein aayega).
const person = {
name: "Aarav",
greet: function() {
return "Hello, I'm " + this.name;
},
// Shorthand syntax (ES6+):
greetShort() {
return "Hi, " + this.name;
}
};
console.log(person.greet()); // "Hello, I'm Aarav"Tip: greetShort() jaisa shorthand syntax (bina "function" keyword ke) modern JavaScript mein bahut common hai — same functionality, less typing.