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Arrays

Array is a data structure for storing and manipulating collections of indexed values. Arrays are used to store ordered data collections such as a list of resorts, products, hotel guests, etc.

Creation​

An array is declared with the opening and closing square brackets [], array literals. Inside the brackets, each array element is separated by a comma.

const clients = ["Mango", "Poly", "Ajax"];

Access to elements​

To access the values of array elements, use syntax with square brackets, array[index]. There should be no space between the name of the variable storing the array and the brackets.

const clients = ["Mango", "Poly", "Ajax"];

// By specifying the element index in brackets, you get its value
console.log(clients[0]); // Mango
console.log(clients[1]); // Poly
console.log(clients[2]); // Ajax

Array elements are indexed starting at zero.

array indices

Overriding​

Unlike strings, array elements can be changed if you access them by index and assign a different value.

const clients = ["Mango", "Poly", "Ajax"];
clients[0] = "Kiwi";
clients[1] = "Pango";
console.log(clients); // ["Kiwi", "Pango", "Ajax"]

Array length​

The length of an array, that is, the number of its elements, is stored in the length property. It is a dynamic value that changes automatically when elements are added or removed.

const clients = ["Mango", "Poly", "Ajax"];
console.log(clients.length); // 3

Last element's index​

Most often, we do not know in advance the length of an array. In order to get the value of the last element, use the following approach: the array length is always the index of the last element + 1. Using the formula array_length - 1, you can get the value of the last element of any array with arbitrary length.

const clients = ["Mango", "Poly", "Ajax"];
const lastElementIndex = clients.length - 1;
console.log(lastElementIndex); // 2
console.log(clients[lastElementIndex]); // "Ajax"