NodeList
objects are collections of nodes such as those returned by {{domxref("Node.childNodes")}} and the {{domxref("document.querySelectorAll")}} method.
Although NodeList
is not an Array
, it is possible to iterate on it using forEach()
. Older browsers doesn't implement this method yet.
Properties
- {{domxref("NodeList.length")}}
- The number of nodes in the
NodeList
.
Methods
- {{domxref("NodeList.item()", "NodeList.item(idx)")}}
- Returns an item in the list by its index, or
null
if the index is out-of-bounds; can be used as an alternative to simply accessingnodeList[idx]
(which instead returnsundefined
whenidx
is out-of-bounds). - {{domxref("NodeList.entries()")}}
- Returns an {{jsxref("Iteration_protocols","iterator")}} allowing to go through all key/value pairs contained in this object.
- {{domxref("NodeList.forEach()")}}
- Executes a provided function once per
NodeList
element. - {{domxref("NodeList.keys()")}}
- Returns an {{jsxref("Iteration_protocols", "iterator")}} allowing to go through all keys of the key/value pairs contained in this object.
- {{domxref("NodeList.values()")}}
- Returns an {{jsxref("Iteration_protocols", "iterator")}} allowing to go through all values of the key/value pairs contained in this object.
Description
A sometimes-live collection
In some cases, the NodeList
is a live collection, which means that changes in the DOM are reflected in the collection. For example, {{domxref("Node.childNodes")}} is live:
var parent = document.getElementById('parent'); var child_nodes = parent.childNodes; console.log(child_nodes.length); // let's assume "2" parent.appendChild(document.createElement('div')); console.log(child_nodes.length); // should output "3"
In other cases, the NodeList
is a static collection, meaning any subsequent change in the DOM does not affect the content of the collection. {{domxref("document.querySelectorAll")}} returns a static NodeList
.
It's good to keep this distinction in mind when you choose how to iterate over the items in the NodeList
, and how you cache the length of the list in particular.
Example
It's possible to loop over the items in a NodeList
using:
for (var i = 0; i < myNodeList.length; ++i) { var item = myNodeList[i]; // Calling myNodeList.item(i) isn't necessary in JavaScript }
Don't be tempted to use for...in
or for each...in
to enumerate the items in the list, since that will also enumerate the length and item properties of the NodeList
and cause errors if your script assumes it only has to deal with {{domxref("element")}} objects. Also, for..in
is not guaranteed to visit the properties in any particular order.
for...of
loops will loop over NodeList
objects correctly, in browsers that support for...of
(like Firefox 13 and later):
var list = document.querySelectorAll( 'input[type=checkbox]' ); for (var item of list) { item.checked = true; }
Specifications
Specification | Status | Comment |
---|---|---|
{{SpecName('DOM WHATWG', '#interface-nodelist', 'NodeList')}} | {{ Spec2('DOM WHATWG') }} | |
{{SpecName('DOM4', '#interface-nodelist', 'NodeList')}} | {{ Spec2('DOM4') }} | |
{{SpecName('DOM3 Core', 'core.html#ID-536297177', 'NodeList')}} | {{ Spec2('DOM3 Core') }} | |
{{SpecName('DOM2 Core', 'core.html#ID-536297177', 'NodeList')}} | {{ Spec2('DOM2 Core') }} | |
{{SpecName('DOM1', 'level-one-core.html#ID-536297177', 'NodeList')}} | {{ Spec2('DOM1') }} | Initial definition. |
Browser compatibility
Feature | Chrome | Firefox (Gecko) | Internet Explorer | Opera | Safari |
---|---|---|---|---|---|
Basic support | {{CompatVersionUnknown}} | {{CompatVersionUnknown}} | {{CompatVersionUnknown}} | {{CompatVersionUnknown}} | {{CompatVersionUnknown}} |
entries() , keys() , values() , forEach() |
{{CompatUnknown}} | {{CompatGeckoDesktop("50.0")}} | {{CompatUnknown}} | {{CompatUnknown}} | {{CompatUnknown}} |
Feature | Android | Android Webview | Firefox Mobile (Gecko) | Firefox OS (Gecko) | IE Mobile | Opera Mobile | Safari Mobile | Chrome for Android |
---|---|---|---|---|---|---|---|---|
Basic support | {{CompatVersionUnknown}} | {{CompatVersionUnknown}} | {{CompatVersionUnknown}} | {{CompatVersionUnknown}} | {{CompatVersionUnknown}} | {{CompatVersionUnknown}} | {{CompatVersionUnknown}} | {{CompatVersionUnknown}} |
entries() , keys() , values() , forEach() |
{{CompatUnknown}} | {{CompatUnknown}} | {{CompatGeckoMobile("50.0")}} | {{CompatUnknown}} | {{CompatUnknown}} | {{CompatUnknown}} | {{CompatUnknown}} | {{CompatUnknown}} |