onclick Attribute

Where to use the onclick Attribute

Description

The onclick attribute is a common attribute which may be used on most elements to specify script to be executed when the element is clicked, i.e. there is a "mousedown" followed by a "mouseup" over the same element.

For an element which would ordinarily perform an action when clicked (e.g. input type="submit") this default action can be prevented (in script-enabled user agents) by returning false from its onclick handler. Note that form submission (or reset) can also be prevented by returning false from the onsubmit (or onreset) handlers of the form element itself.

See also the onmouseup, onmousedown and ondblclick attributes.

If you use this attribute (or any attributes of Type Script) the MIME type of the scripting language used should always be provided in a Content-Script-Type HTTP header.

It is good practice not to use these attributes, however, and instead to include external scripts (via script elements) which add any handlers unobtrusively. This makes code more self-contained and also the XHTML is easier to maintain if it doesn't contain any events attributes.