Javascript

Array

An array in JavaScript is a data structure used to store multiple values in a single variable. It can hold various data types and allows for dynamic resizing. Elements are accessed by their index, starting from 0.

 

let x = [10,20,30,40,50];

console.log(x);

console.log(x[0]);

console.log(x[3]);

console.log(x[1]);

let y = Array(22,33,44,55,66)

console.log(y[2])

 

x[6]= 60;

console.log(x);

x[5]= 66;

console.log(x);

x[5]= 606;

console.log(x);

 

for(z in x){

  console.log(z)

}

for(k of x){

  console.log(k)

}

Array predefined function

    JavaScript array methods are built-in functions that allow efficient manipulation and traversal of arrays. They provide essential functionalities like adding, removing, and transforming elements, as well as searching, sorting, and iterating through array elements, enhancing code readability and productivity.

 

Array length

    The length property returns the length of the given array.

Array toString()

    The toString() method converts the given value into the string.

Array join()

    This join() method creates and returns a new string by concatenating all elements of an array. It uses a specified separator between each element in the resulting string.

Array pop()

Array push()

Array shift()

Array unshift()

Array concat()

Array splice()

Array slice()

delete array[index]

    The delete operator is used to delete the given value which can be an object, array, or anything.

 

let x = [10, 20, 30, 40, 50];

console.log(x);

console.log(x.length);

console.log(x.toString());

console.log(x.pop())

console.log(x);

console.log(x.push(60,70,80));

console.log(x);

console.log(x.shift());

console.log(x);

console.log(x.unshift(5,6,7));

console.log(x);

 

 Slice,splice,join,concat

 

let x = [10, 20, 30, 40, 50];

console.log(x);

// index strats at 0;

// position strats at 1;

slice(Index,position)

 

console.log(x.slice(2, 3));

Splice(index,how many to delete,what to add))

console.log(x.splice(2, 1, 45, 65));

console.log(x);

//join(Seperaor)

console.log(x.join(" * "));

//concat  creates a new array by merging (concatenating) existing arrays

let y = [11, 22, 33, 44, 55];

console.log(x.concat(y));

console.log(y.concat(x));

 

Search functions

let x = [10, 20, 30, 40, 50,40,60,40];

//indexOf searches an array for an element value and returns its position.

console.log(x.indexOf(40))

//To find out the last occurence of the element

console.log(x.lastIndexOf(40))

//IT checks wether the element is present in the array or not

console.log(x.includes(66))

 

myarray.find((value)=>{

    if(value > 40){

        console.log(value)

    }

})

//50,40,60,40

 

console.log(x.findLast((value)=>{

  return value>40;

}))

 

Sort functions

array.sort()

let books = ["math", "science", "social", "engljsh", "english","hindi"];

console.log(books);

console.log(books.sort());

console.log(books);

console.log(books.reverse());

console.log(books);

let myarray = [10,20,30,40,50,60,70,80,90,100,101];

console.log(myarray.sort((firstelement,secondelement)=>{

  return (firstelement-secondelement)

}));

Array Iteration Functions

let myarray = [11, 22, 33, 44, 55, 66, 77, 88, 99];

var Total = 0;

myarray.forEach((value, index, array) => {

  var Total = Total + value;

  console.log(Total);

});

 

console.log(

  myarray.map((value) => {

    //return value*3;

  }),

);

 

myarray.filter((value)=>{

    if(value > 20){

        console.log(value)

    }

})

//22, 33, 44, 55, 66, 77, 88, 99

console.log(

  myarray.reduce((Total, value, index, array) => {

    return (Total = Total + value);

  }),

);

let yourarray = [101, 203, 303, 404];

 

Multidimentionl Array

let combinedArray = [myarray, yourarray];

//console.log(combinedArray);

spread operator

let combinedSpreadArray = [...myarray, ...yourarray];

//To merge an array we use spread operator

//console.log(combinedSpreadArray);

insert and remove element without using any predefined method

var myarray = [10, 20, 30, 40, 50];

for (i = 0; i < myarray.length; i++) {

  console.log(myarray[i]);

}

//How to add an element at the begening of an array

console.log(myarray);

myarray[5] = myarray[4];

myarray[4] = myarray[3];

myarray[3] = myarray[2];

myarray[2] = myarray[1];

myarray[1] = myarray[0];

myarray[0] = 44;

console.log(myarray);

 

//How to add an element at the end of an array

myarray[myarray.length] = 155;

 

//How to add an element at the specified position  of an array

//30,55

//[10, 20, 30,40, 50 ]

//[10, 20, 30 ,40, 50, ]