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web api instance property

Element: className property

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The className property of the Element interface gets and sets the value of the class attribute of the specified element.

Value

A string variable representing the class or space-separated classes of the current element.

Examples

const el = document.getElementById("item");
el.className = el.className === "active" ? "inactive" : "active";

Notes

The name className is used for this property instead of class because of conflicts with the “class” keyword in many languages which are used to manipulate the DOM.

className can also be an instance of SVGAnimatedString if the element is an SVGElement. It is easier to get/set the class attribute of an element using getAttribute and setAttribute if you are dealing with SVG elements. However, take into account that getAttribute returns null instead of "" if the element has an empty class attribute.

elm.setAttribute("class", "my-class");
const myClass = elm.getAttribute("class");

[!NOTE] class is the name of an HTML Attribute, while className is the name of a DOM Property.

Specifications

SpecificationsStandards references are available on the canonical MDN page.

Browser compatibility

Browser compatibilityCompatibility data is available on the canonical MDN page.

See also