Object Basics

Program demonstrating object creation and manipulation

BeginnerTopic: Object Programs

JavaScript Object Basics Program

This program helps you to learn the fundamental structure and syntax of JavaScript programming.

// Method 1: Object literal
let person = {
    name: "John",
    age: 30,
    city: "New York"
};

console.log("Person:", person);
console.log("Name:", person.name);
console.log("Age:", person.age);

// Method 2: Adding properties
person.email = "john@example.com";
person["phone"] = "123-456-7890";

console.log("\nAfter adding properties:", person);

// Method 3: Object with methods
let calculator = {
    num1: 10,
    num2: 5,
    add: function() {
        return this.num1 + this.num2;
    },
    subtract: function() {
        return this.num1 - this.num2;
    },
    multiply() {  // ES6 shorthand
        return this.num1 * this.num2;
    }
};

console.log("\nCalculator:");
console.log("Add:", calculator.add());
console.log("Subtract:", calculator.subtract());
console.log("Multiply:", calculator.multiply());

// Method 4: Object constructor
function Person(name, age) {
    this.name = name;
    this.age = age;
    this.greet = function() {
        return "Hello, I'm " + this.name;
    };
}

let person1 = new Person("Alice", 25);
let person2 = new Person("Bob", 30);

console.log("\nPerson 1:", person1.greet());
console.log("Person 2:", person2.greet());

// Method 5: Object.keys, Object.values, Object.entries
let student = {
    name: "Jane",
    grade: "A",
    subjects: ["Math", "Science"]
};

console.log("\nObject methods:");
console.log("Keys:", Object.keys(student));
console.log("Values:", Object.values(student));
console.log("Entries:", Object.entries(student));

// Method 6: Object destructuring
let { name, age } = person;
console.log("\nDestructured:", name, age);

// Method 7: Spread operator
let personCopy = { ...person };
personCopy.age = 31;
console.log("\nOriginal:", person.age);
console.log("Copy:", personCopy.age);

Output

Person: { name: 'John', age: 30, city: 'New York' }
Name: John
Age: 30

After adding properties: { name: 'John', age: 30, city: 'New York', email: 'john@example.com', phone: '123-456-7890' }

Calculator:
Add: 15
Subtract: 5
Multiply: 50

Person 1: Hello, I'm Alice
Person 2: Hello, I'm Bob

Object methods:
Keys: [ 'name', 'grade', 'subjects' ]
Values: [ 'Jane', 'A', [ 'Math', 'Science' ] ]
Entries: [ [ 'name', 'Jane' ], [ 'grade', 'A' ], [ 'subjects', [ 'Math', 'Science' ] ] ]

Destructured: John 30

Original: 30
Copy: 31

Understanding Object Basics

This program demonstrates object creation and manipulation in JavaScript.

Method 1: Object Literal

Simplest way to create object:

let obj = {
    key: value,
    key2: value2
};

Method 2: Adding Properties

Two ways to add:

•Dot notation: obj.property = value

•Bracket notation: obj["property"] = value

Bracket notation useful for:

•Dynamic property names

•Properties with special characters

•Properties stored in variables

Method 3: Object Methods

Functions as object properties:

let obj = {
    method: function() {
    },
    shorthand() {  // ES6

        return this.property;
    }
};

        return this.property;

`this` keyword:

•Refers to the object itself

•Context-dependent

Method 4: Constructor Function

Create multiple objects:

function Person(name, age) {
    this.name = name;
    this.age = age;
}
let person = new Person("John", 30);

Method 5: Object Methods

Built-in Object methods:

•Object.keys(obj): Array of keys

•Object.values(obj): Array of values

•Object.entries(obj): Array of [key, value] pairs

Method 6: Destructuring

Extract properties:

let { name, age } = person;

Method 7: Spread Operator

Shallow copy:

let copy = { ...original };

When to Use:

Literal

: Simple objects, one-time use

Constructor

: Multiple similar objects

Class

: Modern OOP (ES6)

Spread

: Copying, merging objects

Let us now understand every line and the components of the above program.

Note: To write and run JavaScript programs, you need to set up the local environment on your computer. Refer to the complete article Setting up JavaScript Development Environment. If you do not want to set up the local environment on your computer, you can also use online IDE to write and run your JavaScript programs.

Practical Learning Notes for Object Basics

This JavaScript program is part of the "Object Programs" topic and is designed to help you build real problem-solving confidence, not just memorize syntax. Start by understanding the goal of the program in plain language, then trace the logic line by line with a custom input of your own. Once you can predict the output before running the code, your understanding becomes much stronger.

A reliable practice pattern is to run the original version first, then modify only one condition or variable at a time. Observe how that single change affects control flow and output. This deliberate style helps you understand loops, conditions, and data movement much faster than copying full solutions repeatedly.

For interview preparation, explain this solution in three layers: the high-level approach, the step-by-step execution, and the time-space tradeoff. If you can teach these three layers clearly, you are ready to solve close variations of this problem under time pressure.

Classes (ES6)