Arrays in JS

What is Array?

• Array is a special type of object used to store multiple items under a single variable name.

Example:

Without an array:

let fruit1 = "Apple";
let fruit2 = "Mango";
let fruit3 = "Pineapple";
let fruit4 = "Guava";

With an array:

let fruits=["Apple", "Mango", "Pineapple", "Guava"];

Characteristics:

Zero-indexed: The first element starts at index 0.
Dynamic size: Arrays can automatically grow or shrink.
Heterogeneous: They can hold mixed data types (numbers, strings, objects, or other arrays).
Mutable: Arrays are mutable.

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Creating a Array:

The most common way to create an array is using array literals [].

// Creating array

const students=["Raksha" , "Rakshan" , "Ranjani" , "Varun"];
console.log(students);

[ 'Raksha', 'Rakshan', 'Ranjani', 'Varun' ]

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Accessing Array Elements :

• Elements in the array are accessed using their index.
• Index starts from 0.

let fruits = ["Apple", "Mango", "Pineapple" , "Guava"];

console.log(fruits[0]); 
console.log(fruits[1]); 
console.log(fruits[2]); 
console.log(fruits[3]); 

Apple
Mango
Pineapple
Guava

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Updating Array Elements:

We can update an array element by accessing its index and assigning a new value to it.

Example:

let fruits = ["Apple", "Mango", "Pineapple", "Guava"];

fruits[3] = "Banana";

console.log(fruits);

Output:

[ 'Apple', 'Mango', 'Pineapple', 'Banana' ]

Here, the fruits[3]="Guava" is changed to "Banana".

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Finding the Array Length:

The length property returns the number of elements in the array.

Example:

let fruits = ["Apple", "Mango", "Pineapple", "Guava"];
console.log(fruits.length);

Output:

4

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Arrays can store heterogeneous data:

What is heterogeneous array?

Heterogeneous data means storing different types of values in the same array.

Example:

let data = ["Raksha", 23, true, 10.5, null];

console.log(data);

Output:

[ 'Raksha', 23, true, 10.5, null ]

Here the array contains different data types:

Value	Data Type
"Raksha"	String
23	Number
true	Boolean
10.5	Number
null	Null

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Loop for Arrays:

for Loop

The traditional for loop is used when you want to access the index of each array element.

Example:

let fruits = ["Apple", "Mango", "Pineapple", "Guava"];

for (let i = 0; i < fruits.length; i++) {
    console.log(fruits[i]);
}

Output:

Apple
Mango
Pineapple
Guava

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Adding Elements to an Array Without Functions:

We can add an element to an array without using a function by assigning a value to an index that is equal to or greater than the current array length.

Example:

// Adding element without functions

let zoo=["Lion" , "Tiger" , "Parrot" , "Peacock" , "Monkey"];
console.log(zoo);
zoo[zoo.length]="King cobra";
console.log(zoo);

Output:

[ 'Lion', 'Tiger', 'Parrot', 'Peacock', 'Monkey' ]

[ 'Lion', 'Tiger', 'Parrot', 'Peacock', 'Monkey', 'King cobra' ]

How does zoo[zoo.length] work?

Initially:

Index:    0        1        2         3         4
          ↓        ↓        ↓         ↓         ↓
Value:   Lion     Tiger    Parrot    Peacock   Monkey

The array has 5 elements, so: zoo.length =5

Therefore:

zoo[zoo.length] = "King cobra";

is equivalent to:

zoo[5] = "King cobra";

Now:

After adding "King cobra":

Index:    0        1        2         3         4          5
          ↓        ↓        ↓         ↓         ↓          ↓
Value:   Lion     Tiger    Parrot    Peacock   Monkey    King cobra

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