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2026-03-09 14:12 Diff
https://htmlacademy.org/courses/javascript-programming/arrays/summary-1

An array is a data type that is a list of elements, each of which has its own sequence number.

In the array you can store any data: strings, Boolean values, numbers and even other arrays.

Numbering of array elements starts from zero, therefore the sequence number (index) of the first element equals zero.

You can use a variable as an index.

Use the [].length command to calculate array length (how many elements it has). You can use it to get the last element of the array.

var numbers = [1, 2, 3, 4, 5]; var index = 3; // Will log 1 in the console console.log(numbers[0]); // Will log 4 in the console console.log(numbers[index]); // Will log 5 in the console console.log(numbers.length); // Will log 5 in the console console.log(numbers[numbers.length - 1]);

Arrays can be sorted in loops. For example, the loop below logs array elements in the console one by one and stops working when i becomes equal to the length of the array.

var numbers = [1, 2, 3, 4, 5]; for (var i = 0; i < numbers.length; i++) { console.log(numbers[i]); } // Will log 1 // Will log 2 // Will log 3 // Will log 4 // Will log 5

Writing to an array is done in the same way as reading: by using square brackets.

var numbers = []; var index = 1; numbers[0] = 1; numbers[index] = 2; // Will log [1,2] in the console console.log(numbers);
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