Forem: SIYAMALA G

Array Search

SIYAMALA G — Sun, 19 Apr 2026 07:33:11 +0000

Array Search means finding a value inside an array.

1. includes()

=>checks if value exists

const a=[2,99,45,76,54];

console.log(a.includes(45));
console.log(a.includes(12));

//true
//false

2. indexOf()

=>finds indexvalue and it print first occurrence

const a=[2,99,45,76,45,54];

console.log(a.indexOf(45));

2  //first occurance

3.lastIndexOf()

=>same as indexOf but it print last occurance

const a=[2,99,45,76,45,54];

console.log(a.lastIndexOf(45));

4 //last occurance

4.find()

=>finds value with condition and return first matching value.
=>check from frist(start->end).

const a=[2,99,45,76,54];
const b=a.find(n=>n>40);
console.log(b);

5.findLast()

=>same as find but it check from last (end->start)

const a=[2,99,45,76,54];
const b=a.find(n=>n>40);
console.log(b);

6.findIndex()

=>find indexvalue with condition.
=>return first matching indexvalue.

const a=[2,9,4,7,14];
const b=a.findIndex(n=>n>40);
console.log(b);

const a=[2,8,4,77,14];
const b=a.findIndex(n=>n>40);
console.log(b);

-1  //no match

3

7.findLastIndex()

=>same as findIndex but it return last matching indexvalue.

const a=[2,9,4,6,8];
const b=a.findLastIndex(n=>n>5);
console.log(b);

Array Iterations

SIYAMALA G — Sat, 18 Apr 2026 13:33:16 +0000

What is Iteration?
It is a repeating process,usually with the aim of approaching a desired result.

filter()
creating a new array containing only the element that pass a specific condition.

let a=["apple","grap","banana","watermelon"];
let b=a.filter((x)=>(x.length>6));
console.log(b);

watermelon

flatMap()
first map all the element in the array,Then create new array.

let a=[2,7,3,1,0];
let b =a.flatMap((x)=>[x,x+1]);
console.log(b);

2,3,7,8,3,4,1,2,0,1

reduce()
procees the array and return single value.

let num=[2,7,3,1,0];
let a=num.reduce(x);

function x(c,d){
T=c+d;
return T;
}
console.log(a);

13  //(2+7=>9+3=>12+1=>13+0=13)

reduceRight()
same as reduce but it is work from (right-to-left) opposite direction.

let num =["h","e","l","l","o"];
let a=num.reduce(sum);
let b=num.reduceRight(sum);

function sum(x,y){
return x+y;
}
console.log(a);
console.log(b);

hello
olleh

every()
it return false ==> condition not satisfied
otherwise,it return true.(like AND operator)

let a=[4,8,11];
let b =a.every((a)=>(a%2==0);
console.log(b);

false

some()
if it is return false ==> no one is sastisfied the condition otherwise,it is return true(like OR operator)

let a=[2,5,7,9,11];
let b=a.some((a)=>(a%2==0));
console.log(b);

true

from()(To be discussed)
create a new copied array from iterable object.

let a="TEASHOP";
let b=Array.from(a);
console.log(b);

"T","E","A","S","H","O","P"

keys()
object type==>return keys
array type==>return values(index value)

const a={
   age:35,
   id:1258,
   height:5.2,

 };
  const b=Object.keys(a);
  console.log(b);

age
id
height

another example

const a=[5,8,9,3];
    const b=a.keys();
    console.log(...b);

entries()
it's return both index and values of an array

const a=[5,8,9,3];
const b=a.entries();
console.log([...b]);

[0,5]
[1,8]
[2,9]
[3,3]

with()
create a new array by changing/replace one element at a specific index without modifying the original array.

 const a=[5,8,"hel",3];
 const b=a.with(2,"hello");
 console.log(b);

5,8,hello,3

CALLBACK FUNCTION- EXAMPLES

SIYAMALA G — Thu, 16 Apr 2026 13:22:03 +0000

What is callback Function ?
A function that you pass into another function, so it can be used (called) later.

1.Bus Travel :

function conductor(ticket){
    console.log("where to go");
     ticket();
}

function passenger()
{
    console.log("Ooty");
}

conductor(passenger);

OUTPUT:

where to go
Ooty

2.G-pay process :

function Gpay(money){
    console.log("enter the amount");
    money();
}

function PIN(){
    console.log("enter the 4 digit PIN");
}

function credit(){
    console.log("sucessfully credited");
}
Gpay(PIN);
credit();

OUTPUT:

enter the amount
enter the 4 digit PIN
sucessfully credited

3.Login Process:

function Web(signin){
    console.log("Email/Mobile no");
    signin();
}

function password(){
    console.log("enter your password");
}

function OTP(){
    console.log("enter otp");
}

function Login(){
    console.log("Sucessfully Login");
}
Web(password);
OTP();
Login();

OUTPUT:

Email/Mobile no
enter your password
enter otp
Sucessfully Login

4.ClassRoom Attendance

function ClassA(attendance){
    console.log("Roll no 1");
}

function ask(){
    console.log("Aishwarya present");
}

function student1(){
    consolee.log("Rool.no 2");
}

function student2(){
    console.log("Bharathi present");
}
ClassA(ask);
student1();
student2();

OUTPUT:

Roll.no 1
Aishwarya present
Roll.no 2
Bharathi present

5.ATM Machine Process

function ATM(Transaction){   
   console.log("domestic/International");
   Transaction();
 }
function step1(){
   console.log("click domestic");
 }
function step2(){
   console.log("click withdraw");
}
function step3(){
   console.log("enter your pin");
}
function step4(){
      console.log("enter the amount");
}
function step5(){
      console.log("collect your amount");
}
 function step6(){
      console.log("THANK YOU");
 }
 ATM(step1);
 step2();
 step3();
 step4();
 step5();
 step6();

OUTPUT:

Domestic/International
click domestic
click withdraw
enter your pin
enter the amount
collect your amount
THANK YOU