PreventDefault

PreventDefault is a method on Event objects in the Document Object Model (DOM). It cancels the default action the browser would normally perform for the event. After calling it, the browser will not navigate to a link, submit a form, or perform other standard actions associated with the event.

Common uses include suppressing the default behavior of anchor tags, form submissions, and certain keyboard or mouse events. For example, in an event handler you can call e.preventDefault() to stop a link from navigating, while allowing your own logic to run. It is also used to implement custom form validation or dynamic user interfaces that replace default browser behavior.

PreventDefault only stops the default action; it does not stop event propagation. To stop propagation through the DOM, use e.stopPropagation() or e.stopImmediatePropagation() if needed. In inline event handlers, returning false can in some environments prevent default actions, but this is not reliable in modern standards, so explicit calls to preventDefault and stopPropagation are preferred.

Compatibility and alternatives: preventDefault is supported in all modern browsers. For very old environments, a common fallback is to check for the method and set a legacy property, such as if (e.preventDefault) e.preventDefault(); else e.returnValue = false.

See also: stopPropagation, stopImmediatePropagation, returnValue, Event interface.