jQuery .attr()
Learn all about the jQuery function .attr().
The .attr() method gets the attribute value for only the first element in the matched set. To get the value for each element individually, use a looping construct such as jQuery’s .each() or .map() method.
Using jQuery’s .attr() method to get the value of an element’s attribute has two main benefits:
- Convenience: It can be called directly on a jQuery object and chained to other jQuery methods.
- Cross-browser consistency: The values of some attributes are reported inconsistently across browsers, and even across versions of a single browser. The
.attr()method reduces such inconsistencies.
Note: Attribute values are strings with the exception of a few attributes such as value and tabindex.
As of jQuery 1.6, the .attr() method returns undefined for attributes that have not been set. To retrieve and change DOM properties such as the checked, selected, or disabled state of form elements, use the .prop() method.
Attributes vs. Properties
The difference between attributes and properties can be important in specific situations. Before jQuery 1.6, the .attr() method sometimes took property values into account when retrieving some attributes, which could cause inconsistent behavior. As of jQuery 1.6, the .prop() method provides a way to explicitly retrieve property values, while .attr() retrieves attributes.
For example, selectedIndex, tagName, nodeName, nodeType, ownerDocument, defaultChecked, and defaultSelected should be retrieved and set with the .prop() method. Prior to jQuery 1.6, these properties were retrievable with the .attr() method, but this was not within the scope of attr. These do not have corresponding attributes and are only properties.
Concerning boolean attributes, consider a DOM element defined by the HTML markup <input type="checkbox" checked="checked" />, and assume it is in a JavaScript variable named elem:
elem.checked |
true (Boolean) Will change with checkbox state |
|---|---|
$( elem ).prop( "checked" ) |
true (Boolean) Will change with checkbox state |
elem.getAttribute( "checked" ) |
"checked" (String) Initial state of the checkbox; does not change |
$( elem ).attr( "checked" ) (1.6) |
"checked" (String) Initial state of the checkbox; does not change |
$( elem ).attr( "checked" ) (1.6.1+) |
"checked" (String) Will change with checkbox state |
$( elem ).attr( "checked" ) (pre-1.6) |
true (Boolean) Changed with checkbox state |
According to the W3C forms specification, the checked attribute is a boolean attribute, which means the corresponding property is true if the attribute is present at all—even if, for example, the attribute has no value or is set to empty string value or even "false". This is true of all boolean attributes.
Nevertheless, the most important concept to remember about the checked attribute is that it does not correspond to the checked property. The attribute actually corresponds to the defaultChecked property and should be used only to set the initial value of the checkbox. The checked attribute value does not change with the state of the checkbox, while the checked property does. Therefore, the cross-browser-compatible way to determine if a checkbox is checked is to use the property:
-
if ( elem.checked ) -
if ( $( elem ).prop( "checked" ) ) -
if ( $( elem ).is( ":checked" ) )
The same is true for other dynamic attributes, such as selected and value.