DOM HTMLCollection

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HTMLCollection

An HTMLCollection is an array-like collection (list) of HTML elements.

The elements in a collection can be accessed by index (starts at 0).

The length Property returns the number of elements in the collection.

HTMLCollection vs NodeList

An HTMLCollection is almost the same as a NodeList.

See the description below.

WHO Returns an HTMLCollection?

The getElementsByTagName() Method

The getElementsByClassName() Method

The children Property

Properties and Methods

The following properties and methods can be used on an HTMLCollection:

Name	Description
length	Returns the number of elements in an HTMLCollection
item()	Returns the element at a specified index
namedItem()	Returns the element with a specified id

Examples

Example

Get all parapgraphs:

const elements = document.getElementsByTagName("p");

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Example

The number of <p> elements in the document are:

const elements = document.getElementsByTagName("p");
let numb = elements.length;

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Example

Loop over the elements in an HTMLCollection:

const elements = document.getElementsByTagName("*");
for (let i = 0; i < elements.length; i++) {
.. some code ..
}

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Not an Array

An HTMLCollection is not an Array!

An HTMLCollection may look like an array, but it is not.

You can loop through an HTMLCollection and refer to its elements with an index.

But you cannot use Array methods like push(), pop(), or join() on an HTMLCollection.

The Difference Between an HTMLCollection and a NodeList

A NodeList and an HTMLcollection is very much the same thing.

Both are array-like collections (lists) of nodes (elements) extracted from a document. The nodes can be accessed by index numbers. The index starts at 0.

Both have a length property that returns the number of elements in the list (collection).

An HTMLCollection is a collection of document elements.

A NodeList is a collection of document nodes (element nodes, attribute nodes, and text nodes).

HTMLCollection items can be accessed by their name, id, or index number.

NodeList items can only be accessed by their index number.

An HTMLCollection is always a live collection. Example: If you add a <li> element to a list in the DOM, the list in the HTMLCollection will also change.

A NodeList is most often a static collection. Example: If you add a <li> element to a list in the DOM, the list in NodeList will not change.

The getElementsByClassName() and getElementsByTagName() methods return a live HTMLCollection.

The querySelectorAll() method returns a static NodeList.

The childNodes property returns a live NodeList.

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