DOM: NodeList vs HTMLCollection

By Xah Lee. Date: . Last updated: .

Difference Between NodeList, HTMLCollection

NodeList is a collection of nodes. Node includes any HTM/XML element, and also text content of a element, such as inner text of <p>…</p>.

HTMLCollection is a collection any HTM/XML elements. It has method namedItem, which is not in NodeList. (Opera browser adds the method to its NodeList object.)

Array-Like Object

• NodeList and HTMLCollection are array-like objects. Meaning, they have length property, and have properties named 0, 1, 2, …, n, so that you can access its elements like a array.

To use array methods on array-like object, call the method like this:

Array.prototype.array_method_name.call(array-like_object, function)

[see JS: Array-Like Object]

[see JS: Array-Like Object to Array]

[see JS: Array.prototype]

Live Object or No?

• NodeList and HTMLCollection are NOT ALWAYS live objects. For example: document.querySelectorAll return a non-live object. [see DOM: Get Elements by ID, Tag, Name, Class, CSS Selector]

• There's no builtin way to find out whether NodeList or HTMLCollection is live object.

• When working with live objects, you must be careful, not to insert or remove element within a loop. [see DOM: What Does Live Object Mean?]

You should NOT use for (var x in object) {…}, because that loops thru all enumerable properties and goes into prototype chain. [see JS: Access Property]

The most supported and safe and fast way to loop thru array-like object is a normal loop, like this:

for (let i = 0; i < myNodeList.length; ++i) {… myNodeList[i] …}

How to Convert Array-Like Object to Array?

See: JS: Array-Like Object to Array

What Does getElementsByClassName Return?

As of , {Firefox, Internet Explorer} return HTMLCollection. {Chrome, Safari, Opera} return NodeList. Older versions of Firefox returns NodeList.

[see DOM: Get Elements by ID, Tag, Name, Class, CSS Selector]

Even Browsers and W3C Are Confused!

Here's what Mozilla says:

Note: While the W3C DOM 3 Core specification says elements is a NodeList that was simply because of a an attempt to have the “core” specification not depend on the “html” specification at that time. The DOM 4 draft says that elements is an HTMLCollection.

Gecko/Firefox currently returns a NodeList (Bug 162927) but starting with Gecko/Firefox 19, this method will return HTMLCollection (Bug 799464). Internet Explorer returns a HTMLCollection. WebKit returns a NodeList. Opera also returns a NodeList, but with a namedItem method implemented, which makes it similar to a HTMLCollection.

, from https://developer.mozilla.org/en-US/docs/Web/API/Element.getElementsByTagName

Here's WHATWG says as of 2016-07-02:

Elements is the better solution for representing a collection of elements. HTMLCollection is an historical artifact we cannot rid the web of.

However, as of today , Google Chrome and Firefox returns HTMLCollection.

You can find out the type by:

Object.prototype.toString.call(document .getElementsByClassName("xyz"))

Web Scripting Overview

  1. Browser Window Object, Document Object Model
  2. Intro to Event-Based Programing
  3. JavaScript Load Order
  4. What is Live Object
  5. NodeList vs HTMLCollection
  6. DOM: Whitespace Nodes
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JavaScript in Depth

Basics

  1. JavaScript Basics
  2. true, false
  3. Operators
  4. Branch Control
  5. Loop
  6. Array Basics
  7. Object Basics
  8. RegExp Basics

Variable

  1. Value Types
  2. let
  3. const
  4. var
  5. var Order
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  8. Destructuring Assignment

String

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Function

  1. Define Function
  2. Arrow Function ⭐
  3. Function Params
  4. “arguments” Object
  5. Rest Params ⭐
  6. Arg Default Value ⭐
  7. Arg Destructure ⭐
  8. f Declaration vs Expression
  9. Closure
  10. f call apply bind
  11. Functional Programing

Object Property

  1. Property Overview
  2. Property Key
  3. Dot vs Bracket Notation
  4. Create/Delete Property
  5. Get/Set Property
  6. Check Property Existence
  7. Access Property
  8. List Properties
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  11. Property Descriptor
  12. Symbol

Object and Inheritance

  1. Object Overview
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  11. Clone Object
  12. Test Object Equality
  13. Add Method to Prototype

Array

  1. Understand JS Array
  2. Create Array
  3. Sparse Array
  4. Array-Like Object
  5. Array How-To

Class

  1. “this” Binding
  2. What's Constructor?
  3. Property Key "prototype"
  4. Operator “new”
  5. Operator “instanceof”
  6. Property Key “constructor”
  7. Class
  8. Keyword “extends”
  9. Keyword “super”

Iterable ⭐

  1. Interface
  2. Iterable
  3. Iterator
  4. Iterator Prototype
  5. for-of Loop
  6. Spread Operator
  7. Generator
  8. Generator Function

Misc

  1. Set Object
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  3. Try Catch Throw Finally
  4. Import/Export
  5. Promise
  6. Proxy
  7. ES2015 Features
  8. How to Convert ES5 to ES2015
  9. Style Guide
  10. Semicolon Rules
  11. Exclamation Before Function
  12. How to Determine Strict Mode?
  13. x.y.z Associativity
  14. Function Chain
  15. Random Number, Range, Integer, Element
  16. Timing JS Code
  17. Range Function for Array
  18. Random Array Element, Randomize Array
  19. Tagged Template String
  20. String to Number
  21. Format Number

Object Reference

  1. the Global Object
  2. Object 🙼 Object.prototype
  3. Array 🙼 Array.prototype
  4. Function 🙼 Function.prototype
  5. String 🙼 String.prototype
  6. RegExp 🙼 RegExp.prototype 🙼 RegExp Syntax
  7. Date 🙼 Date.prototype
  8. Set ⭐🙼 Set.prototype
  9. Map ⭐🙼 Map.prototype
  10. JSON
  11. Math
  12. Reflect
  13. Symbol ⭐🙼 Symbol.prototype
  14. Number 🙼 Number.prototype
  15. Boolean 🙼 Boolean.prototype

DOM How-To

  1. Basic DOM Methods
  2. Get Elements by ID, Tag, Name, Class, CSS Selector
  3. Change CSS
  4. Change Node Content
  5. Create/Insert Node
  6. Remove Node
  7. Get Element's Attribute Value
  8. Set Element's Attribute Value
  9. Remove Element's Attribute Value
  10. List/Add/Remove Class Attribute
  11. Add/Remove Event Handler
  12. Navigate DOM Tree

DOM Overview

  1. Browser Window Object, Document Object Model
  2. Intro to Event-Based Programing
  3. JavaScript Load Order
  4. What is Live Object
  5. NodeList vs HTMLCollection
  6. DOM: Whitespace Nodes

Basic DOM Methods

  1. Basic DOM Methods
  2. Node Type, Name, Value
  3. Navigate DOM Tree

HTML Form

  1. HTML Form
  2. Visit URL in a New Window
  3. Instant Field Validation
  4. Input Field Validation
  5. HTML: Input Range Slider

DOM How To

  1. Encode URL, Escape String
  2. Browser Info, Navigator Object
  3. Get URL (window.location)
  4. Web Cookies
  5. Web Storage
  6. Find Window Width
  7. Find Element Width
  8. WebSocket

Web Scripting Examples

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  2. document.write
  3. Image Rollover
  4. Pop-up New Window
  5. Digital Clock
  6. Stopwatch
  7. Fade a Element
  8. Fade a Element Using CSS Transition
  9. Shake Element
  10. How to Create Tooltip
  11. Falling Snow Effect
  12. JavaScript: Floating Box Following Scroll

DOM Misc

  1. Value of “this” in Event Handler
  2. Event Delegation
  3. Get Current Script Tag
  4. insertAfter Element
  5. Randomize List
  6. create Document Fragment
  7. innerHTML, nodeValue, textContent, innerText?

jQuery

  1. jQuery Basics
  2. jQuery() vs querySelectorAll()
  3. Write JQuery Plugin

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