Arrays

In JavaScript, an array is an object that stores a collection of elements. Arrays can store elements of any data type, including other arrays, and can be dynamically resized. Each element in an array is assigned a unique index, starting from 0.

Syntax:

arrayName = [element1, element2, element3, ...];

where arrayName is the name you give to the array, and element1, element2, element3, etc. are the values you want to store in the array.

Built-In Methods

• length: returns the number of elements in the array.
• push(): adds one or more elements to the end of the array.
• pop(): removes the last element from the array and returns it.
• shift(): removes the first element from the array and returns it.
• unshift(): adds one or more elements to the beginning of the array.
• splice(): removes elements from the array and/or adds new elements.
• concat(): joins two or more arrays and returns a new array.
• slice(): extracts a portion of an array and returns a new array.
• indexOf(): returns the index of the first occurrence of a specified element in the array.
• forEach(): calls a function for each element in the array.
• map(): creates a new array with the results of calling a function for each element in the array.
• filter(): creates a new array with all elements that pass a test implemented by a function.
• reduce(): applies a function to each element in the array to reduce the array to a single value.

Examples :

1. push() , splice () :let myArray = ["apple", "banana", "cherry"]; console.log(myArray.length); // outputs 3 myArray.push("date"); console.log(myArray); // outputs ["apple", "banana", "cherry", "date"] myArray.splice(1, 1, "orange"); console.log(myArray); // outputs ["apple", "orange", "cherry", "date"]

Output

3
[ 'apple', 'banana', 'cherry', 'date' ]
[ 'apple', 'orange', 'cherry', 'date' ]

2. map() : const numbers = [1, 2, 3, 4, 5]; const squaredNumbers = numbers.map(num => num * num); console.log(squaredNumbers); // Output: [1, 4, 9, 16, 25]

Output

[ 1, 4, 9, 16, 25 ]

3. reduce() :const numbers = [1, 2, 3, 4, 5]; const sum = numbers.reduce((acc, num) => acc + num, 0); console.log(sum); // Output: 15

Output

15

4. filter() :const numbers = [1, 2, 3, 4, 5]; const evenNumbers = numbers.filter(num => num % 2 === 0); console.log(evenNumbers); // Output: [2, 4]

Output

[ 2, 4 ]