DOM Node Lists

JavaScript HTML DOM Node Lists

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The HTML DOM NodeList Object

A NodeList object is a list (collection) of nodes extracted from a document.
A NodeList object is almost the same as an HTMLCollection object.
Some (older) browsers return a NodeList object instead of an HTMLCollection for methods like getElementsByClassName().
All browsers return a NodeList object for the property childNodes. 
Most browsers return a NodeList object for the method querySelectorAll().
The following code selects all <p> nodes in a document:

Example

var myNodeList = document.querySelectorAll("p");

The elements in the NodeList can be accessed by an index number.
To access the second <p> node you can write:

y = myNodeList[1];

Note: The index starts at 0.

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HTML DOM Node List Length

The length property defines the number of nodes in a node list:

Example

var myNodelist = document.querySelectorAll("p");
document.getElementById("demo").innerHTML = myNodelist.length;

Example explained:

1. Create a list of all <p> elements
2. Display the length of the list

The length property is useful when you want to loop through the nodes in a node list:

Example

Change the background color of all <p> elements in a node list:

var myNodelist = document.querySelectorAll("p");
var i;
for (i = 0; i < myNodelist.length; i++) {
    myNodelist[i].style.backgroundColor = "red";
}

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The Difference Between an HTMLCollection and a NodeList

An HTMLCollection (previous chapter) is a collection of HTML elements.
A NodeList is a collection of document nodes.
A NodeList and an HTML collection is very much the same thing.
Both an HTMLCollection object and a NodeList object is an array-like list (collection) of objects.
Both have a length property defining the number of items in the list (collection).
Both provide an index (0, 1, 2, 3, 4, ...) to access each item like an array.
HTMLCollection items can be accessed by their name, id, or index number.
NodeList items can only be accessed by their index number.
Only the NodeList object can contain attribute nodes and text nodes.

A node list is not an array!
A node list may look like an array, but it is not.
You can loop through the node list and refer to its nodes like an array.
However, you cannot use Array Methods, like valueOf(), push(), pop(), or join() on a node list.

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