Calculate the size of an array containing non-consecutive indices

Question

Calculate the size of an array containing non-consecutive indices

Have you ever noticed how JavaScript's .length property calculates the length of an array by adding one to the last numerical index? Do you know a solution for accurately determining the element length of arrays with non-consecutive indexes?

//Perfectly works with consecutively indexed array length!
var test_array = [4,5,6,7,8];
$('#indexed-array').html("Consecutively Indexed Array Length: " + test_array.length);

//Trouble arises with unconsecutively indexed arrays!
var test_array = [];
test_array[1] = 1;
test_array[3] = 2;
test_array[7] = 3;
$('#unconsecutive-indexed-array').html("Unconsecutively Indexed Array Length: " + test_array.length);

<script src="https://ajax.googleapis.com/ajax/libs/jquery/2.1.1/jquery.min.js"></script>
<p id="indexed-array">
</p>

<p id="unconsecutive-indexed-array">
</p>

javascript arrays

Answer 1

Answer №1

One way to determine the length of an array is by using Object.keys

var numbers = [];
numbers[1] = 1;
numbers[3] = 3;
console.log(numbers.length); // Output: 4
console.log(Object.keys(numbers).length); // Output: 2

Object.keys can also be utilized to access an object's keys/properties.

var obj = {a:'a', b:'b'};
Console.log(Object.keys(obj)); // Output: ["a", "b"]
var items = [1,2,3];
console.log(Object.keys(items)); // Output: ["0", "1", "2"]

Answer 2

One way to determine the length of an array is by using Object.keys

var numbers = [];
numbers[1] = 1;
numbers[3] = 3;
console.log(numbers.length); // Output: 4
console.log(Object.keys(numbers).length); // Output: 2

Object.keys can also be utilized to access an object's keys/properties.

var obj = {a:'a', b:'b'};
Console.log(Object.keys(obj)); // Output: ["a", "b"]
var items = [1,2,3];
console.log(Object.keys(items)); // Output: ["0", "1", "2"]

Answer 3

Answer №2

To calculate the count in an array, you can utilize the Array#reduce method.

var test_array = [, 1, , 2, , , , 7],
    count = test_array.reduce(r => r + 1, 0);

console.log(count);

Answer 4

To calculate the count in an array, you can utilize the Array#reduce method.

var test_array = [, 1, , 2, , , , 7],
    count = test_array.reduce(r => r + 1, 0);

console.log(count);

Answer 5

Answer №3

Utilize Array#filter as it processes only those elements in an array that have a value assigned (regardless of the value itself).

The Callback function is called for indexes of the array which contain assigned values; it does not apply to indexes that are deleted or were never assigned any value. Elements in the array that do not meet the callback condition are skipped and are not added to the new array.[Ref]

var test_array = [4, 5, 6, 7, 8];
$('#indexed-array').html("Consecutively Indexed Array Length: " + test_array.length);
var test_array = [];
test_array[1] = 0; //falsey values are not ignored
test_array[3] = 2;
test_array[7] = 3;
test_array[11] = undefined; //falsey values are not ignored
var filteredArray = test_array.filter(Object); //OR test_array.filter(function(){ return true; })
$('#unconsecutive-indexed-array').html("Unconsecutively Indexed Array Length: " + filteredArray.length);

<script src="https://ajax.googleapis.com/ajax/libs/jquery/2.1.1/jquery.min.js"></script>
<p id="indexed-array"></p>
<p id="unconsecutive-indexed-array"></p>

Answer 6

Utilize Array#filter as it processes only those elements in an array that have a value assigned (regardless of the value itself).

The Callback function is called for indexes of the array which contain assigned values; it does not apply to indexes that are deleted or were never assigned any value. Elements in the array that do not meet the callback condition are skipped and are not added to the new array.[Ref]

var test_array = [4, 5, 6, 7, 8];
$('#indexed-array').html("Consecutively Indexed Array Length: " + test_array.length);
var test_array = [];
test_array[1] = 0; //falsey values are not ignored
test_array[3] = 2;
test_array[7] = 3;
test_array[11] = undefined; //falsey values are not ignored
var filteredArray = test_array.filter(Object); //OR test_array.filter(function(){ return true; })
$('#unconsecutive-indexed-array').html("Unconsecutively Indexed Array Length: " + filteredArray.length);

<script src="https://ajax.googleapis.com/ajax/libs/jquery/2.1.1/jquery.min.js"></script>
<p id="indexed-array"></p>
<p id="unconsecutive-indexed-array"></p>

Calculate the size of an array containing non-consecutive indices

Answer №1

Answer №2

Answer №3

Similar questions

Express app unable to receive data from Ajax request

Encountering a 'DiscordAPIError: Unknown interaction' error while attempting to share details about a command

Utilizing Selenium with Python to choose a specific option from a dropdown selection

Knockout does not have the ability to automatically create a dropdown menu from an array property within an object when using the "foreach"

Ensure that the Ajax calendar extender does not allow the selection of past dates

Is there a cutting-edge javascript/jquery tool that enables SQL-type queries on JSON datasets?

Pause page scrolling temporarily in JavaScript while allowing the scrollbar to continue scrolling until the pause is lifted

Do all variables need to be converted into objects in order to be executed in JavaScript?

Navigate through a list of data in JSON format

Prioritize loading the JS function before initiating PHP validation

Using blending modes with gradient colors in an SVG design

Retrieve the variable only once a response has been received from the POST request

I would like to retrieve my data using my personal API and have them displayed as checkboxes

Exploring the asynchronous for loop functionality in the express.js framework

Using Three.js to spin a mesh in the direction of a sphere

Retrieve data from a 2-dimensional array using PHP

Utilizing jQuery or JavaScript to transfer information within a Bootstrap modal

Concealing the Footer on Mobile Websites in Muse UI When the Keyboard Appears

What is the best way to display a list of items in Vue JS while maintaining the

Troubleshooting a resizing problem in Angular's ag-grid