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 Path: blob/main/files/en-us/web/api/attr/index.md
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---
title: Attr
slug: Web/API/Attr
page-type: web-api-interface
browser-compat: api.Attr
---

{{APIRef("DOM")}}

The Attr interface represents one of an element's attributes as an object. In most situations, you will directly retrieve the attribute value as a string (e.g., {{domxref("Element.getAttribute()")}}), but certain functions (e.g., {{domxref("Element.getAttributeNode()")}}) or means of iterating return Attr instances.

{{InheritanceDiagram}}

The core idea of an object of type Attr is the association between a name and a value. An attribute may also be part of a namespace and, in this case, it also has a URI identifying the namespace, and a prefix that is an abbreviation for the namespace.

The name is deemed local when it ignores the eventual namespace prefix and deemed qualified when it includes the prefix of the namespace, if any, separated from the local name by a colon (:). We have three cases: an attribute outside of a namespace, an attribute inside a namespace without a prefix defined, an attribute inside a namespace with a prefix:

AttributeNamespace nameNamespace prefixAttribute local nameAttribute qualified name
myAttrnonenonemyAttrmyAttr
myAttrmynamespacenonemyAttrmyAttr
myAttrmynamespacemynsmyAttrmyns:myAttr

Note: This interface represents only attributes present in the tree representation of the {{domxref("Element")}}, being a SVG, an HTML or a MathML element. It doesn't represent the property of an interface associated with such element, such as {{domxref("HTMLTableElement")}} for a {{HTMLElement("table")}} element. (See {{Glossary("Attribute", "this article")}} for more information about attributes and how they are reflected into properties.)

Instance properties

This interface also inherits the properties of its parent interfaces, {{domxref("Node")}} and {{domxref("EventTarget")}}.

  • {{domxref("Attr.localName", "localName")}} {{ReadOnlyInline}}

    • : A string representing the local part of the qualified name of the attribute.

  • {{domxref("Attr.name", "name")}} {{ReadOnlyInline}}

    • : The attribute's qualified name. If the attribute is not in a namespace, it will be the same as {{domxref("attr.localName", "localName")}} property.

  • {{domxref("Attr.namespaceURI", "namespaceURI")}} {{ReadOnlyInline}}

    • : A string representing the URI of the namespace of the attribute, or null if there is no namespace.

  • {{domxref("Attr.ownerElement", "ownerElement")}} {{ReadOnlyInline}}

    • : The {{domxref("Element")}} the attribute belongs to.

  • {{domxref("Attr.prefix", "prefix")}} {{ReadOnlyInline}}

    • : A string representing the namespace prefix of the attribute, or null if a namespace without prefix or no namespace are specified.

  • {{domxref("Attr.specified", "specified")}} {{ReadOnlyInline}} {{deprecated_inline}}

    • : This property always returns true.

  • {{domxref("Attr.value", "value")}}

    • : The attribute's value, a string that can be set and get using this property.

Instance methods

This interface has no specific methods, but inherits the methods of its parent interfaces, {{domxref("Node")}} and {{domxref("EventTarget")}}.

Specifications

{{Specifications}}

Browser compatibility

{{Compat}}

See also

  • Other nodes are {{domxref("CDATASection")}}, {{domxref("CharacterData")}}, {{domxref("Comment")}}, {{domxref("Document")}}, {{domxref("Element")}}, {{domxref("ProcessingInstruction")}}, and {{domxref("Text")}}.