Attr

Baseline Widely available

This feature is well established and works across many devices and browser versions. It’s been available across browsers since July 2015.

TheAttr 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.,Element.getAttribute()), but some cases may require interacting withAttr instances (e.g.,Element.getAttributeNode()).

The core idea of an object of typeAttr is the association between aname and avalue. An attribute may also be part of anamespace 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 deemedlocal when it ignores the eventual namespace prefix and deemedqualified 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:

Attribute	Namespace name	Namespace prefix	Attribute local name	Attribute qualified name
`myAttr`	none	none	`myAttr`	`myAttr`
`myAttr`	`mynamespace`	none	`myAttr`	`myAttr`
`myAttr`	`mynamespace`	`myns`	`myAttr`	`myns:myAttr`

Note:This interface represents only attributes present in the tree representation of theElement, being a SVG, an HTML or a MathML element. It doesn't represent theproperty of an interface associated with such element, such asHTMLTableElement for a<table> element. (Seethis article for more information about attributes and how they arereflected into properties.)

Instance properties

This interface also inherits the properties of its parent interfaces,Node andEventTarget.

localNameRead only: A string representing the local part of the qualified name of the attribute.
nameRead only: The attribute'squalified name. If the attribute is not in a namespace, it will be the same aslocalName property.
namespaceURIRead only: A string representing the URI of the namespace of the attribute, ornull if there is no namespace.
ownerElementRead only: TheElement the attribute belongs to.
prefixRead only: A string representing the namespace prefix of the attribute, ornull if a namespace without prefix or no namespace are specified.
specifiedRead onlyDeprecated: This property always returnstrue.
value: The attribute's value, a string that can be set and get using this property.