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JavaScript - Array

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• JavaScript - Array
  • Array
    • Creating an Array
    • Accessing Array Elements
    • Changing an Array Element
    • Adding New Elements
  • .length:Length of Array
  • Looping Array Elements
    • for loop
    • .forEach() function

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Array

• Array:

  • a special variable, which can hold more than one value.

• Arrays are a special type of objects.

  • typeof array_name returns object

• Array can have variables of different data types.

  myArray[0] = Date.now;
  myArray[1] = myFunction;
  myArray[2] = myCars;
  

• The Difference Between Arrays and Objects

  • In JavaScript, arrays use numbered indexes.
  • In JavaScript, objects use named indexes.

• The elements in an array can be different types.

  let arr = [1, "2", null, { name: "John" }];
  console.log(arr); //[ 1, '2', null, { name: 'John' } ]
  

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Creating an Array

• Using const

  • It defines a constant reference to an array.
  • Because of this, we can still change the elements of a constant array.

• Syntax

// Using an array literal
const array_name = [item1, item2, ...];

// create an empty array, and then provide the elements
const array_name = [];
array_name[0]= item1;
array_name[1]= item2;
array_name[2]= item3;

// Using Array object
const array_name = new Array(item1, item2, ...);

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Accessing Array Elements

• Syntax

// access an item
let var_name = array_name[index];
array_name[0]; //the first item
array_name[-1]; //the last item

// Access the Full Array
let var_name = array_name;

• Array indexes start with 0.
• the full array can be accessed by referring to the array name.

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Changing an Array Element

• Syntax

array_name[index] = value;

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Adding New Elements

• Using the push() method

console.log("\n-------- Array: .push() --------\n");

const fruits = ["Banana", "Orange", "Apple"];
fruits.push("Lemon"); // Adds a new element (Lemon) to fruits

console.log(fruits); //[ 'Banana', 'Orange', 'Apple', 'Lemon' ]

• Using the length property and index

console.log("\n-------- Array: [length] --------\n");

const fruits = ["Banana", "Orange", "Apple"];
fruits[fruits.length] = "Lemon"; // Adds a new element (Lemon) to fruits

console.log(fruits); //[ 'Banana', 'Orange', 'Apple', 'Lemon' ]

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.length:Length of Array

const fruits = ["Banana", "Orange", "Apple", "Mango"];
let length = fruits.length; //4

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Looping Array Elements

for loop

console.log("\n-------- Array: for loop --------\n");
const fruits = ["Banana", "Orange", "Apple", "Mango"];

for (let i = 0; i < fruits.length; i++) {
  console.log(i, fruits[i]);
}
// 0 Banana
// 1 Orange
// 2 Apple
// 3 Mango

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.forEach() function

console.log("\n-------- Array: .forEach() --------\n");
const fruits = ["Banana", "Orange", "Apple", "Mango"];

fruits.forEach((ele) => {
  console.log(ele);
});
// Banana
// Orange
// Apple
// Mango

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