Arrays

An Array is an object that allows storing multiple values in a single variable. Indices start at 0.

Basic Operations

const fruits = ["Apple", "Banana"];

fruits.push("Orange"); // Adds at the end
fruits.pop(); // Removes the last
fruits.unshift("Pear"); // Adds at the beginning
fruits.shift(); // Removes the first

console.log(fruits.length); // Size of the array

Modification and Copy

• slice(start, end): Creates a copy of a portion of the array without modifying the original.
• splice(start, count, item1...): Changes the content by removing, replacing, or adding elements. Modifies the original.

Modern Methods (Higher Order)

These are the most powerful for working with data:

• map(): Transforms each element and returns a new array.
• filter(): Creates a new array with elements that meet a condition.
• reduce(): Reduces the array to a single value (e.g.: sum everything).
• forEach(): Executes a function for each element.
• join(): Joins all elements into a text string.
• includes(): Checks if a value exists in the array.

Example:

const numbers = [1, 2, 3, 4, 5];
const even = numbers.filter(n => n % 2 === 0); // [2, 4]
const doubled = numbers.map(n => n * 2); // [2, 4, 6, 8, 10]