Forem: Praveen Kumar K

Methods in JavaScript?

Praveen Kumar K — Wed, 08 Apr 2026 16:55:34 +0000

push() → Add element at end Adds a new element to the end of the array.[]

let fruits = ["apple", "banana"];
fruits.push("mango");

console.log(fruits);

👉 Output:

["apple", "banana", "mango"]

pop() → Remove last element Removes the last item from the array.

JavaScript

let fruits = ["apple", "banana", "mango"];
fruits.pop();

console.log(fruits);

👉 Output:

["apple", "banana"]

✔️ Use when removing the latest item

🔹 3. shift() → Remove first element

Removes the first element.

JavaScript

let fruits = ["apple", "banana", "mango"];
fruits.shift();

console.log(fruits);
// ["banana", "mango"]

👉 Use when removing from start

🔹 4. unshift() → Add at beginning

Adds element to the start of array.

JavaScript

let fruits = ["banana", "mango"];
fruits.unshift("apple");

console.log(fruits);
// ["apple", "banana", "mango"]

👉 Use when adding at start

🔹 5. length → Find array size
Gives total number of elements.

JavaScript

let fruits = ["apple", "banana", "mango"];
console.log(fruits.length);
// 3

👉 Useful for loops and counting

🔹 6. includes() → Check value exists

Checks if a value is present in array.

JavaScript

let fruits = ["apple", "banana", "mango"];
console.log(fruits.includes("banana"));
// true

👉 Returns true or false

🔹 7. indexOf() → Find position

Returns index (position) of element.

JavaScript

let fruits = ["apple", "banana", "mango"];
console.log(fruits.indexOf("mango"));
// 2

👉 If not found → returns -1

🔹 8. join() → Convert array to string

Joins all elements into a string.

JavaScript

let fruits = ["apple", "banana", "mango"];
console.log(fruits.join(", "));
// "apple, banana, mango"

👉 Useful for displaying data

🔹 9. slice() → Get part of array
Returns a portion of array (does not change original).

JavaScript

let fruits = ["apple", "banana", "mango"];
console.log(fruits.slice(0, 2));
// ["apple", "banana"]

👉 Start index included, end index excluded

🔹 10. splice() → Add/Remove elements

Changes the original array.

JavaScript

let fruits = ["apple", "banana", "mango"];
fruits.splice(1, 1);

console.log(fruits);
// ["apple", "mango"]

👉 Syntax:

JavaScript

array.splice(start, deleteCount, newItem)

What is constructor in JavaScript?

Praveen Kumar K — Tue, 07 Apr 2026 14:06:11 +0000

In JavaScript, a constructor is a special function used to create and initialize objects.
Simple idea

A constructor is like a blueprint for creating multiple similar objects.

Constructor function (old/classic way):

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

const p1 = new Person("Praveen", 25);
const p2 = new Person("Kumar", 30);

console.log(p1.name); // Praveen

Key points:

The function name usually starts with a capital letter.
The new keyword is used to call the constructor.
this refers to the new object being created.

Constructor in ES6 class (modern way):

class Person {
constructor(name, age) {
this.name = name;
this.age = age;
}
}

const p1 = new Person("Praveen", 22);

Here:

constructor() is a special method inside a class.
It runs automatically when you create an object with new.

What happens when you use new?
When you do:

const p = new Person("Praveen", 22);

JavaScript:

Creates a new empty object
Sets this to that object
Runs the constructor function
Returns the object.

(TBD)

pop()
shift()
unshift()
forEach()
map()
filter()
reduce()
find()
findIndex()

What is object?

Praveen Kumar K — Mon, 06 Apr 2026 11:25:05 +0000

An object is a collection of data stored as key–value pairs.

✅ Example:

JavaScript:

let person = {
name: "Praveen",
age: 22,
city: "Chennai"
};

console.log(person.name); // Praveen

👉 Here:
name, age, city → keys
"Praveen", 22, "Chennai" → values

Object Inside Object (Nested Object):

Program:

Output:

What is Function and it's types?

Praveen Kumar K — Sun, 05 Apr 2026 18:11:04 +0000

A function is a block of code designed to perform a specific task. It runs only when it is called (invoked), and it helps make code reusable, clean, and easy to manage.

Program:

function greet(name) {
return "Hello " + name;
}

console.log(greet("Praveen"));

✔ Output:

Hello Praveen

Types of Functions (in JavaScript)

Function Declaration: A normal function defined using the function keyword.

Program:

function add(a, b) {
return a + b;
}
✔ Can be called before declaration.

Function Expression: Function stored in a variable.

const multiply = function(a, b) {
return a * b;
};
✔ Cannot be called before definition.

Arrow Function (ES6): Short and modern syntax. Program:

const subtract = (a, b) => a - b;
✔ Clean and simple
✔ No function keyword needed.

Anonymous Function: Function without a name.

Program:

setTimeout(function() {
console.log("Hello");
}, 1000);
✔ Mostly used as arguments.

IIFE (Immediately Invoked Function Expression) Runs immediately after creation.

Program:

(function() {
console.log("Executed immediately");
})();

Callback Function:

A function passed as an argument to another function.

Program:

function processUser(name, callback) {
callback(name);
}

processUser("Praveen", function(name) {
console.log("Hello " + name);
});

Recursive Function: A function that calls itself.

Program:

function factorial(n) {
if (n === 0) return 1;
return n * factorial(n - 1);
}

Define Function in Javascript?

Praveen Kumar K — Fri, 03 Apr 2026 18:12:28 +0000

Step 1:

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.

Step 2:

Calling Functions:

Functions are executed when they are called or invoked
You call a function by adding parentheses to its name: name().

Step 3:

Function Parameters:

Parameters allow you to send values to a function.
Parameters are listed in parentheses in the function definition.

Step 4:

Function Return Values:

A function can return a value back to the code that called it.
The return statement is used to return a value from a function.

Step 5:

Function Arguments:

Function parameters and arguments are distinct concepts.
Parameters are the names listed in the function definition.
Arguments are the values received by the function.

Step 6:

Function Expressions:

A function expression is a function stored in a variable
The variable name can be used to call the function.

Step 7:

Arrow Functions:

Arrow Functions is a short syntax for function expressions.
You can skip the function keyword.
You can skip the return keyword.
You can skip the curly brackets.

For Example:

![ ](https://dev-to-uploads.s3.amazonaws.com/uploads/articles/wg76mxv3uy34yoy80yvy.jpg

Simple Program and Output:

Write a program to find the total marks, average and Grade using while loop.

Praveen Kumar K — Thu, 02 Apr 2026 15:21:18 +0000

PROGRAM:
const marks=[96,65,64,74,80];
let i=0;
let failCount=0;
let total=0;
let average=0;
let j=0;
while(i if(marks[i]<35){
fcount++;
}
i++
}
console.log("FailCount",failCount);
if(failCount>0){
console.log("no grade")
}
else{
j=0;
while(j total+=marks[j];
j++;
}
}
console.log("Total",total);
average=Math.floor(total/marks.length);
console.log("Average",average);
if(failCount==0){
if(average>=90){
console.log("grade A");
}
else if(average>=80){
console.log("grade B");
}
else if(average>=70 ){
console.log("grade C");
}
else if(average>=60){
console.log("grade D");
}
else{
console.log("grade E")
}
}
OUTPUT:
FailCount 0
Total 379
Average 75
grade B

Flowchart for Program:

Flowchart for looping:

Praveen Kumar K — Fri, 27 Mar 2026 09:09:47 +0000

What is JavaScript?

Praveen Kumar K — Thu, 26 Mar 2026 09:43:28 +0000

JavaScript (JS) is a high-level, interpreted programming language mainly used to make websites interactive and dynamic. It runs inside the browser and allows you to control webpage behavior like clicking buttons, showing messages, validating forms, etc.
It is one of the core technologies of the web along with:

•HTML → Structure
•CSS → Styling
•JavaScript → Behavior

Key Features of JavaScript
Client-side scripting (runs in browser)

•Dynamic typing (no need to declare data types)
•Event-driven (responds to user actions like clicks)
•Object-oriented (supports objects and classes)
•Asynchronous (handles tasks like API calls)

Simple JavaScript Code:

<!DOCTYPE html>

JavaScript Example

Hello World

Click Me

function changeText() { document.getElementById("demo").innerHTML = "Text Changed!"; }

Explanation:

•button → When clicked, it calls a function
•changeText() → JavaScript function
•document.getElementById() → Selects HTML element
•innerHTML → Changes the content