NodeList
BaselineWidely available
This feature is well established and works across many devices and browser versions. It’s been available across browsers since July 2015.
NodeList objects are collections ofnodes, usually returned by properties such asNode.childNodes and methods such asdocument.querySelectorAll().
This interface was anattempt to create an unmodifiable list and only continues to be supported to not break code that's already using it. Modern APIs represent list structures using types based on JavaScriptarrays, thus making many array methods available, and at the same time imposing additional semantics on their usage (such as making their items read-only).
These historical reasons do not mean that you as a developer should avoidNodeList. You don't createNodeList objects yourself, but you get them from APIs such asDocument.querySelectorAll(), and these APIs are not deprecated. However, be careful of the semantic differences from a real array.
AlthoughNodeList is not anArray, it is possible to iterate over it withforEach(). It can also be converted to a realArray usingArray.from().
Live vs. Static NodeLists
Although they are both consideredNodeList objects, there are 2 varieties of NodeList:live andstatic.
Live NodeLists
In some cases, theNodeList islive, which means that changes in the DOM automatically update the collection.
For example,Node.childNodes is live:
const parent = document.getElementById("parent");let childNodes = parent.childNodes;console.log(childNodes.length); // let's assume "2"parent.appendChild(document.createElement("div"));console.log(childNodes.length); // outputs "3"Static NodeLists
In other cases, theNodeList isstatic, where any changes in the DOM do not affect the content of the collection. The ubiquitousdocument.querySelectorAll() method returns astaticNodeList.
It's good to keep this distinction in mind when you choose how to iterate over the items in theNodeList, and whether you should cache the list'slength.
Instance properties
NodeList.lengthRead onlyThe number of nodes in the
NodeList.
Instance methods
NodeList.item()Returns an item in the list by its index, or
nullif the index is out-of-bounds.An alternative to accessing
nodeList[i](which instead returnsundefinedwheniis out-of-bounds). This is mostly useful for non-JavaScript DOM implementations.NodeList.entries()Returns an
iterator, allowing code to go through all key/value pairs contained in the collection. (In this case, the keys are integers starting from0and the values are nodes.)NodeList.forEach()Executes a provided function once per
NodeListelement, passing the element as an argument to the function.NodeList.keys()Returns an
iterator, allowing code to go through all the keys of the key/value pairs contained in the collection. (In this case, the keys are integers starting from0.)NodeList.values()Returns an
iteratorallowing code to go through all values (nodes) of the key/value pairs contained in the collection.
Example
It's possible to loop over the items in aNodeList using afor loop:
for (let i = 0; i < myNodeList.length; i++) { let item = myNodeList[i];}Don't usefor...in to enumerate the items inNodeLists, since they willalso enumerate itslength anditem properties and cause errors if your script assumes it only has to deal withelement objects. Also,for...in is not guaranteed to visit the properties in any particular order.
for...of loops overNodeList objects correctly:
const list = document.querySelectorAll("input[type=checkbox]");for (const checkbox of list) { checkbox.checked = true;}Browsers also support the iterator method (forEach()) as well asentries(),values(), andkeys().
Specifications
| Specification |
|---|
| DOM # interface-nodelist |