SetAttribute

setAttribute is a method on DOM elements that sets or updates the value of a named attribute on an element. It takes two string arguments: the attribute name and the new value. If the attribute did not previously exist, it is created; if it did exist, its value is updated. In HTML documents, the value becomes the string representation of the provided value. For boolean attributes (such as disabled, checked, or selected), the presence of the attribute is what matters: setting a value with setAttribute generally enables the attribute, while removing the attribute disables it.

For XML or when namespaces are involved, there is a separate method called setAttributeNS that allows specifying a namespace URI and a qualified name. Without a namespace, setAttribute uses the element’s default namespace context and applies to attributes in that context.

setAttribute is distinct from property assignment. Many attributes map to DOM properties; for example, an element’s id or className can be changed via element.id or via setAttribute("id","..."). However, properties and attributes are not always kept in perfect sync, and updating one may not produce identical effects in all cases. If you need to remove an attribute, use removeAttribute. In practice, setAttribute offers a straightforward way to manage an element’s attribute values across HTML and XML contexts.