attr
A função attr()
do CSS é utilizada para se obter o valor de um determinado atributo do elemento selecionado e usá-lo na folha de estilo. Também pode ser utilizado em pseudo-elementos, nesse caso o valor do atributo no pseudo-elemento do elemento original é retornado.
/* Uso Simples */
attr(data-count);
attr(title);
/* Com o tipo */
attr(src url);
attr(data-count number);
attr(data-width px);
/* Com fallback */
attr(data-count number, 0);
attr(src url, '');
attr(data-width px, inherit);
attr(data-something, 'default');
Nota: A função attr()
pode ser utilizada com qualquer propriedade CSS, mas o suporte para propriedades que não sejam content
é experimental.
Sintaxe
Valores
nome-do-atributo
-
É o nome do atributo HTML do elemento referenciado no CSS.
<tipo-ou-unidade>
Experimental-
É uma palavra-chave representando tanto o tipo quanto o valor do atributo, ou sua unidade, assim como no HTML alguns atributos tem unidades implícitas. Se o uso de
<tipo-ou-unidade>
como um valor para determinado atributo for inválido, a expressãoattr()
será inválida também. Se omitida, o padrão serástring
. A lista de valores válidos é:Palavra-chave Tipo Associado Comentário Valor Padrão string
<string>
O valor do atributo é tratado como um CSS <string>
. NÃO será reparado, e em particular os caracteres usados .An empty string. cor
Experimental<color>
O valor do atributo é analisado como hash (3- ou 6-valores hash) ou a palavra-chave. Precisa ser um valor <string>
CSS válido. Os espaços do lead e trail são retirados.corAtual url
Experimental<url>
The attribute value is parsed as a string that is used inside a CSS url()
function. Relative URL are resolved relatively to the original document, not relatively to the style sheet. Leading and trailing spaces are stripped.The url about:invalid
that points to a non-existent document with a generic error condition.integer
Experimental<integer>
The attribute value is parsed as a CSS <integer>
. If it is not valid, that is not an integer or out of the range accepted by the CSS property, the default value is used. Leading and trailing spaces are stripped.0
, or, if0
is not a valid value for the property, the property's minimum value.number
Experimental<number>
The attribute value is parsed as a CSS <number>
. If it is not valid, that is not a number or out of the range accepted by the CSS property, the default value is used. Leading and trailing spaces are stripped.0
, or, if0
is not a valid value for the property, the property's minimum value.length
Experimental<length>
The attribute value is parsed as a CSS <length>
dimension, that is including the unit (e.g.12.5em
). If it is not valid, that is not a length or out of the range accepted by the CSS property, the default value is used. If the given unit is a relative length,attr()
computes it to an absolute length. Leading and trailing spaces are stripped.0
, or, if0
is not a valid value for the property, the property's minimum value.em
,ex
,px
,rem
,vw
,vh
,vmin
,vmax
,mm
,cm
,in
,pt
, orpc
Experimental<length>
The attribute value is parsed as a CSS <number>
, that is without the unit (e.g.12.5
), and interpreted as a<length>
with the specified unit. If it is not valid, that is not a number or out of the range accepted by the CSS property, the default value is used. If the given unit is a relative length,attr()
computes it to an absolute length. Leading and trailing spaces are stripped.0
, or, if0
is not a valid value for the property, the property's minimum value.angle
Experimental<angle>
The attribute value is parsed as a CSS <angle>
dimension, that is including the unit (e.g.30.5deg
). If it is not valid, that is not an angle or out of the range accepted by the CSS property, the default value is used. Leading and trailing spaces are stripped.0deg
, or, if0deg
is not a valid value for the property, the property's minimum value.deg
,grad
,rad
Experimental<angle>
The attribute value is parsed as a CSS <number>
, that is without the unit (e.g.12.5
), and interpreted as an<angle>
with the specified unit. If it is not valid, that is not a number or out of the range accepted by the CSS property, the default value is used. Leading and trailing spaces are stripped.0deg
, or, if0deg
is not a valid value for the property, the property's minimum value.time
Experimental<time>
The attribute value is parsed as a CSS <time>
dimension, that is including the unit (e.g.30.5ms
). If it is not valid, that is not a time or out of the range accepted by the CSS property, the default value is used. Leading and trailing spaces are stripped.0s
, or, if0s
is not a valid value for the property, the property's minimum value.s
,ms
Experimental<time>
The attribute value is parsed as a CSS <number>
, that is without the unit (e.g.12.5
), and interpreted as an<time>
with the specified unit. If it is not valid, that is not a number or out of the range accepted by the CSS property, the default value is used. Leading and trailing spaces are stripped.0s
, or, if0s
is not a valid value for the property, the property's minimum value.frequency
Experimental<frequency>
The attribute value is parsed as a CSS <frequency>
dimension, that is including the unit (e.g.30.5kHz
). If it is not valid, that is not a frequency or out of the range accepted by the CSS property, the default value is used.0Hz
, or, if0Hz
is not a valid value for the property, the property's minimum value.Hz
,kHz
Experimental<frequency>
The attribute value is parsed as a CSS <number>
, that is without the unit (e.g.12.5
), and interpreted as a<frequency>
with the specified unit. If it is not valid, that is not a number or out of the range accepted by the CSS property, the default value is used. Leading and trailing spaces are stripped.0Hz
, or, if0Hz
is not a valid value for the property, the property's minimum value.%
Experimental<percentage>
The attribute value is parsed as a CSS <number>
, that is without the unit (e.g.12.5
), and interpreted as a<percentage>
. If it is not valid, that is not a number or out of the range accepted by the CSS property, the default value is used. If the given value is used as a length,attr()
computes it to an absolute length. Leading and trailing spaces are stripped.0%
, or, if0%
is not a valid value for the property, the property's minimum value. <fallback>
Experimental-
The value to be used if the associated attribute is missing or contains an invalid value. The fallback value must be valid where
attr()
is used, even if it is not used, and must not contain anotherattr()
expression. Ifattr()
is not the sole component value of a property, its<fallback>
value must be of the type defined by<type-or-unit>
. If not set, CSS will use the default value defined for each<type-or-unit>
.
Sintaxe formal
<attr()> =
attr( <attr-name> <attr-type>? , <declaration-value>? )
<attr-name> =
[ <ident-token> '|' ]? <ident-token>
<attr-type> =
string |
ident |
color |
number |
percentage |
length |
angle |
time |
frequency |
flex |
<dimension-unit>
Exemplos
HTML
<p data-foo="hello">world</p>
CSS
p::before {
content: attr(data-foo) " ";
}
Resultado
Especificações
Specification |
---|
CSS Values and Units Module Level 5 # attr-notation |
Compatibilidade com navegadores
BCD tables only load in the browser