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JavaScript Objects - Object Keys, Values, Add, Update, Delete

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What is an Object?

  1. An object is a variable that stores data in key-value pairs
  2. It is used to store related data together

Example:


let userDetails = {
name: "anil",
age: 29,
city: "Delhi"
}

  1. name, age, city → keys
  2. "anil", 29, "Delhi" → values


Why Use Objects Instead of Arrays?

  1. Arrays store simple lists
  2. Objects store structured and related data

Example problem with array:


let users = ["anil", 29, "Delhi"];

  1. Hard to understand what 29 represents


Better with object:


let user = {
name: "anil",
age: 29,
city: "Delhi"
}

  1. Clear meaning of each value


How to Access Object Data

Dot Notation


userDetails.name


Bracket Notation


userDetails["age"]


Dynamic Key (Important)


let key = "age";
userDetails[key]


Add New Property


userDetails.email = "anil@test.com";


Update Existing Property


userDetails.name = "anil sidhu";


Delete Property


delete userDetails.city;


Loop Through Object


for (let key in userDetails) {
console.log(key);
console.log(userDetails[key]);
}


Nested Object (Object Inside Object)


let userDetails = {
name: "anil",
age: 29,
address: {
houseNo: 111,
sector: 20,
city: "gurgaon"
}
}


Access Nested Object


userDetails.address.houseNo


Important Concepts to Remember

  1. Object stores data in key-value format
  2. Keys are unique
  3. Values can be string, number, boolean, array, or object


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