JAVASCRIPT PROGRAMMING:Objects
Mastering objects concepts and implementation.
Objects
Objects are collections of key-value pairs where keys are strings (or symbols) and values can be any data type. Objects are fundamental to JavaScript and are used to represent real-world entities.
Creating Objects
Object Literal
let person = {
name: 'John',
age: 30,
city: 'New York',
isStudent: false
};
Object Constructor
let person = new Object();
person.name = 'John';
person.age = 30;
Accessing Object Properties
Dot Notation
console.log(person.name); // 'John'
console.log(person.age); // 30
Bracket Notation
console.log(person['name']); // 'John'
console.log(person['age']); // 30
Object Methods
Objects can contain functions as properties, which are called methods:
let person = {
name: 'John',
age: 30,
greet: function() {
return 'Hello, I am ' + this.name;
},
// ES6 method shorthand
introduce() {
return `Hi, I'm ${this.name} and I'm ${this.age} years old`;
}
};
Object Manipulation
Adding Properties
person.email = 'john@example.com';
person['phone'] = '555-1234';
Modifying Properties
person.age = 31;
person['city'] = 'Boston';
Deleting Properties
delete person.city;
Checking Properties
console.log('name' in person); // true
console.log(person.hasOwnProperty('age')); // true
Object Iteration
for...in Loop
for (let key in person) {
console.log(key + ': ' + person[key]);
}
Object.keys()
let keys = Object.keys(person);
console.log(keys); // ['name', 'age', 'city']
Object.values()
let values = Object.values(person);
console.log(values); // ['John', 30, 'New York']
Object.entries()
let entries = Object.entries(person);
console.log(entries); // [['name', 'John'], ['age', 30], ['city', 'New York']]
Hands-on Examples
Object Basics
let student = {
name: 'Alice',
age: 20,
grade: 'A',
subjects: ['Math', 'Science', 'English']
};
console.log('Name:', student.name);
console.log('Age:', student['age']);
console.log('Grade:', student.grade);
console.log('Subjects:', student.subjects);Objects store data as key-value pairs. You can access properties using dot notation or bracket notation.
Progress