DEV Community: Veera Ganapathi

Javascript Object

Veera Ganapathi — Fri, 17 Jul 2026 07:31:14 +0000

What are JavaScript Objects?

Objects are variables that can store both values and functions.
Values are stored as key:value pairs called properties.
Functions are stored as key:function() pairs called methods.

const students = {
  name:"abc",
  age:18,
  dept:"cs"
};

Object Properties

Properties are key:value Pairs.
A JavaScript object is a collection of properties.
Properties can be changed, added, and deleted.

Access Properties

Dot notation
Bracket notation
Expression

// objectName.property
let age = students.age;

//objectName["property"]
let age = students["age"];

//objectName[expression]
let age = students[x];

Changing Properties

You can change the value of a property:

const person = {
  name: "vijay",
  age :  50
};
person.age = 10;
console.log(person.age);


output:
10

Add New Properties

You can add a new property by simply giving it a value.

const person = {
  name: "vijay",
  age: 50
};
person.nationality = "English";
console.log(person.nationality);

output:
English

Delete Properties

The delete keyword deletes a property from an object.

const person = {
  name: "vijay",
  age: 50
};
delete person.age;
console.log(person);

output:
vijay

The delete keyword deletes both the value and the property.
After deleting, the property is removed. Accessing it will return undefined.

Nested Objects

Property values in an object can be other objects.

const students = {
  name:"abc",
  age:18,
  subject:{
      sub1:"cs",
      sub2:"maths",
      sub3:"cc"
}
};
console.log(students.subject.sub2;);

output:
maths

Object Methods

Methods are actions that can be performed on objects. Methods are functions stored as property values.

const students = {
  name:"abc",
  age:18,
  fullName: function() {
    return students.name + " " + students.age;
  }
};
let full=students.fullName();
console.log(full);

Object Constructors

Sometimes we need to create many objects of the same type. To create an object type we use an object constructor function. It is considered good practice to name constructor functions with an upper-case first letter.

function Person(first, age) {
  this.name = first;
  this.age = age;

}

// Create a Person object
const myFather = new Person("vijay", 50);
const myMother = new Person("thi", 45);
console.log(myFather);
console.log(myMother);

JavaScript Function

Veera Ganapathi — Thu, 16 Jul 2026 01:37:02 +0000

What are Functions?

Functions are reusable code blocks designed for particular tasks. Functions are executed when they are called or invoked. Functions are fundamental in all programming languages

Why Use Functions?

Reuse code (write once, run many times)
Organize code into smaller parts
Make code easier to read and maintain

function welcome() {
  return "Hello World";
}

Function Invocation (Function Call)

Function invocation is the process of calling a function to execute its code.

function greet() {
    console.log("Hello");
}

greet();   // Function Invocation or Function Call

JavaScript Function Parameters

A function invocation executes the statements inside the function by using its name followed by parentheses ().

function add(a, b) {
    console.log(a + b);
}

add(10, 20);   // parentheses(inside the value arguments)

JavaScript Function Return

He return statement is used to send a result back from a function. When return executes, the function stops running at that point. The returned value can be stored in a variable or used directly.

With return

function add(a, b) {
    return a + b;
}

let result = add(10, 20);
console.log(result);

output:
30

Without return

function greet() {
    console.log("Hello");
}

let result = greet();
console.log(result);

output:
Hello
undefined

What is a Function Expression?

A function expression is a function stored in a variable.

// Standard Function
function multiply(a, b) {
  return a * b;
}

// Function Expression
const multiply = function(a, b) {
  return a * b;
};

Hoisting

Function declarations can be called before they are defined.
Function expressions can not be called before they are defined.

JavaScript Arrow Functions

A shorter and simpler way to write a function using the => operator. A concise function syntax introduced in ES6.

//Function Declaration
function add(a, b) {
    return a + b;
}


//Arrow Function
const add = (a, b) => {
    return a + b;
};

JavaScript Loops

Veera Ganapathi — Thu, 16 Jul 2026 00:41:48 +0000

What is loops?

A loop is used to execute a block of code repeatedly until a specified condition becomes false.

Types of Loops in JavaScript

for Loop
while loop
do while

for loop

The for loop is used when the number of iterations is known before the loop starts.

for (let i = 1; i <= 5; i++) {
    console.log(i);
}

while Loop

A while loop executes a block of code repeatedly as long as the given condition is true.

let i = 1;

while (i <= 5) {
    console.log(i);
    i++;
}

do while Loop

A do...while loop executes the code once before checking the condition.

let i = 1;

do {
    console.log(i);
    i++;
} while (i <= 5);

Conditional Statement in Js

Veera Ganapathi — Thu, 16 Jul 2026 00:24:21 +0000

What is conditional statement?

Conditional Statement is used to make decisions in a program based on a condition.

Type:

if
if else
else if
nested if
switch

if Statement

The if statement is used to execute a block of code only when a condition is true.

let age = 20;

if (age >= 18) {
    console.log("Eligible to vote");
}

if else Statement

The if...else statement is used to execute one block of code if the condition is true, and another block if the condition is false.

let age = 16;

if (age >= 18) {
    console.log("Eligible to vote");
} else {
    console.log("Not eligible to vote");
}

else if Statement

The else if statement is used to check multiple conditions and execute the block of the first true condition.

let marks = 85;

if (marks >= 90) {
    console.log("Grade A+");
} else if (marks >= 75) {
    console.log("Grade A");
} else if (marks >= 50) {
    console.log("Pass");
} else {
    console.log("Fail");
}

Nested if Statement

A nested if is an if statement placed inside another if statement. It is used to check multiple dependent conditions.

let age = 20;
let hasID = true;

if (age >= 18) {
    if (hasID) {
        console.log("Eligible to vote");
    } else {
        console.log("ID is required");
    }
} else {
    console.log("Not eligible");
}

switch Statement

The switch statement is used to select one block of code from multiple options based on the value of an expression.

let day = 2;

switch (day) {
    case 1:
        console.log("Monday");
        break;
    case 2:
        console.log("Tuesday");
        break;
    case 3:
        console.log("Wednesday");
        break;
    default:
        console.log("Invalid Day");
}

Operator Js

Veera Ganapathi — Tue, 14 Jul 2026 15:59:43 +0000

What is operator?

JavaScript operators are symbols or keywords used to perform operations on values and variables. Operators are special symbols used to calculate, compare, assign, or check values.

Arithmetic Operators

Arithmetic operators perform arithmetic on numbers (literals or variables).

Operator

+ Addition
- Subtraction
* Multiplication
/ Division
% Modulus (Remainder)

let sum = 5 + 3; // Addition
let diff = 10 - 2; // Subtraction
let p = 4 * 2; // Multiplication
let q = 8 / 2; // Division
let a = 8 % 2; // Modulus
console.log(sum, diff, p, q, a);

Output:
8
8
8
4
0

Assignment Operator

Assignment operators assign values to variables.

let x = 10;

x += 5;  // 15
x -= 3;  // 12
x *= 2;  // 24
x /= 4;  // 6
x %= 5;  // 1

Comparison Operators

Comparison operators are used to compare two values. Comparison operators always return true or false.

5 == "5"   // true (loose equality)
5 === "5"  // false (strict equality)

5 != "5"   // false
5 !== "5"  // true

5 > 3      // true
5 < 3      // false
5 >= 5     // true
5 <= 4     // false

Logical Operators

Logical operators are mainly used to perform the logical operations that determine the equality or difference between the values.

let a = true, b = false;
console.log(a && b); // Logical AND
console.log(a || b); // Logical OR

&& returns true if both operands are true.
|| returns true if at least one operand is true.
! negates the boolean value.

Increment Operator (++)

The increment operator increases the value of a variable by 1.

type

- Pre-Increment (++a)
- Post-Increment (a++)

1. Pre-Increment (++a)

The value is increased first, then used in the expression.

let a = 5;

console.log(++a); // 6
console.log(a);   // 6

2. Post-Increment (a++)

The current value is used first, then increased by 1.

let a = 5;

console.log(a++); // 5
console.log(a);   // 6

Decrement (--) Operators

The decrement operator decreases the value of a variable by 1.

type

Pre-Decrement (--a)
Post-Decrement (a--)

1. Pre-Decrement (--a)

The value is decreased first, then used in the expression.

let a = 5;

console.log(--a); // 4
console.log(a);   // 4

2.Post-Decrement (a--)

The current value is used first, then decreased by 1.

let a = 5;

console.log(a--); // 5
console.log(a);   // 4

JavaScript Basics: Variables and Data Types

Veera Ganapathi — Sat, 11 Jul 2026 08:40:47 +0000

What is Variables ?

JavaScript variables are containers for data. JavaScript variables can be declared in 3 ways:

Using let(Modern JavaScript)
Using const(Modern JavaScript)
Using var (Not Recommended)

1.Let:
The let keyword is introduced in ES6(Version), has block scope and cannot be re-declared in the same scope.

let  n= 10;
n = 20; // Value can be updated
// let n = 15; //can not redeclare
console.log(n)

2. const

The const keyword declares variables that cannot be reassigned. It's block-scoped as well.

const n = 100;
// n = 200; This will throw an error
console.log(n)

3.var
The var keyword is used to declare a variable. It has a function-scoped or globally-scoped behaviour.

var n = 5;
console.log(n);

var n = 20; // reassigning is allowed
console.log(n);

What is Data Type ?

A data type defines the type of value that a variable can store. JavaScript supports various datatypes, which can be broadly categorized into primitive and non-primitive types.

Primitive Data Types:

They can hold a single simple value. String, Number, BigInt, Boolean, undefined, null, and Symbol are primitive data types.

1. Number: Represents numeric values (integers and decimals).

let n = 42;
let pi = 3.14;

2. String: Represents text enclosed in single or double quotes.

let s = "Hello World!";
let a = 'Hello World!';

3. Boolean: Represents a logical value (true or false).

let bool= true;

4. Undefined: A variable that has been declared but not assigned a value.

let notAssigned;
console.log(notAssigned);

5. Null: Represents an intentional absence of any value.

let empty = null;

6. Symbol: Represents unique and immutable values, often used as object keys.

let sym = Symbol('unique');

7. BigInt: A number representing a large integer

let bigNumber = 123456789012345678901234567890n;

Importance of Data Types in JavaScript

Data types are used to identify the type of value stored in a variable. They help JavaScript store, process, and manipulate data correctly.