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---
title: "Enumerated - Glossary | MDN"
chunk: 1/3
source: "https://developer.mozilla.org/en-US/docs/Glossary/Enumerated"
category: "reference"
tags: "web, html, css, javascript, documentation"
date_saved: "2026-05-05T05:30:44.790815+00:00"
instance: "kb-cron"
---
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1. [Glossary](https://developer.mozilla.org/en-US/docs/Glossary)
2. [Enumerated](https://developer.mozilla.org/en-US/docs/Glossary/Enumerated)
# Enumerated
In computer science, an **enumerated** type is a data type consisting of a limited set of named values.
## In this article
* [HTML enumerated attributes](https://developer.mozilla.org/en-US/docs/Glossary/Enumerated#html_enumerated_attributes)
* [ARIA enumerated attributes](https://developer.mozilla.org/en-US/docs/Glossary/Enumerated#aria_enumerated_attributes)
* [JavaScript enumerable properties](https://developer.mozilla.org/en-US/docs/Glossary/Enumerated#javascript_enumerable_properties)
* [See also](https://developer.mozilla.org/en-US/docs/Glossary/Enumerated#see_also)
## [HTML enumerated attributes](https://developer.mozilla.org/en-US/docs/Glossary/Enumerated#html_enumerated_attributes)
In HTML, [enumerated attributes](https://html.spec.whatwg.org/multipage/common-microsyntaxes.html#enumerated-attribute) are attributes with a limited, predefined set of text values. For example, the global HTML [`dir`](https://developer.mozilla.org/en-US/docs/Web/HTML/Reference/Global_attributes/dir) attribute has three valid values: `ltr`, `rtl`, and `auto`. Like for HTML tag names, HTML enumerated attributes and their values are case-insensitive, so `LTR`, `RTL`, and `AUTO` will also work. The IDL-reflected property, [`HTMLElement.dir`](https://developer.mozilla.org/en-US/docs/Web/API/HTMLElement/dir), can also be set using a case-insensitive value, but will always return the canonical format of the value defined in the specification (lowercased values in this example). See [Attribute reflection](https://developer.mozilla.org/en-US/docs/Web/API/Document_Object_Model/Reflected_attributes) for more information.
Each enumerated attribute has a default value for when the attribute is present without a value (the value is missing), and a default value for when the attribute is assigned an invalid value. Unlike [Boolean attribute](https://developer.mozilla.org/en-US/docs/Glossary/Boolean/HTML) HTML attributes — which are always true when the attribute is present whether the value is present, omitted, or invalid — with enumerated HTML attributes, the default for an omitted value may be different from the default for invalid values. For example, the global HTML [`contenteditable`](https://developer.mozilla.org/en-US/docs/Web/HTML/Reference/Global_attributes/contenteditable) attribute has two valid keywords: `true` and `false`. If the attribute is present but no value is set, the value is `true`. If a value is set, but is invalid, such as `contenteditable="contenteditable"`, the value maps to a third state, `inherit`.
## [ARIA enumerated attributes](https://developer.mozilla.org/en-US/docs/Glossary/Enumerated#aria_enumerated_attributes)
ARIA states and properties, being HTML, also have enumerated attributes. If an ARIA attribute includes a both a `true` and `false` value in the enumerated list, it generally treats an omitted attribute as `false` and an invalid value as `true`, while the default value for the empty string or omitted value depends on the attribute.
For example, the `aria-current` attribute accepts a limited list of values that includes `page`, `step`, `location`, `date`, `time`, `true`, and `false`. In this case, if the attribute is not present, is an empty string, is present with no value, or is set to `aria-current="false"` the attribute is false and is not exposed to the user. Any non-empty string value not in the list of enumerated values is treated as if `aria-current="true"` were set.
## [JavaScript enumerable properties](https://developer.mozilla.org/en-US/docs/Glossary/Enumerated#javascript_enumerable_properties)
In JavaScript, enumerable properties are those properties whose internal enumerable flag is set to true, which is the default for properties created via simple assignment or via a property initializer. Most iteration mechanisms (such as [`for...in`](https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Statements/for...in) loops and [`Object.keys`](https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Object/keys)) only visit enumerable keys.
## [See also](https://developer.mozilla.org/en-US/docs/Glossary/Enumerated#see_also)
* [Boolean](https://developer.mozilla.org/en-US/docs/Glossary/Boolean)
* [JavaScript data types and data structures](https://developer.mozilla.org/en-US/docs/Web/JavaScript/Guide/Data_structures)
* [enumerated attributes](https://html.spec.whatwg.org/multipage/common-microsyntaxes.html#enumerated-attribute) in the HTML Standard
* [Attribute reflection](https://developer.mozilla.org/en-US/docs/Web/API/Document_Object_Model/Reflected_attributes)
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