PopStateEvent

PopStateEvent is an event handler for the popstate event on the window.

A popstate event is dispatched to the window every time the active history entry changes between two history entries for the same document. If the history entry being activated was created by a call to history.pushState() or was affected by a call to history.replaceState(), the popstate event's state property contains a copy of the history entry's state object.

Note: Just calling history.pushState() or history.replaceState() won't trigger a popstate event. The popstate event is only triggered by doing a browser action such as a clicking on the back button (or calling history.back() in JavaScript). And the event is only triggered when the user navigates between two history entries for the same document.

Note: Browsers used to handle the popstate event differently on page load, but now they behave the same. Firefox never emitted a popstate event on page load. Chrome did until version 34, while Safari did until version 10.0.

Event PopStateEvent

Syntax

window.onpopstate = funcRef;
  • funcRef is a handler function.

The popstate event

As an example, a page at http://example.com/example.html running the following code will generate alerts as indicated: 

window.onpopstate = function(event) {
  alert("location: " + document.location + ", state: " + JSON.stringify(event.state));
};

history.pushState({page: 1}, "title 1", "?page=1");
history.pushState({page: 2}, "title 2", "?page=2");
history.replaceState({page: 3}, "title 3", "?page=3");
history.back(); // alerts "location: http://example.com/example.html?page=1, state: {"page":1}"
history.back(); // alerts "location: http://example.com/example.html, state: null
history.go(2);  // alerts "location: http://example.com/example.html?page=3, state: {"page":3}

Note that even though the original history entry (for http://example.com/example.html) has no state object associated with it, a popstate event is still fired when we activate that entry after the second call to history.back().

Specifications

Specification
HTML Standard
# the-popstateevent-interface

Browser compatibility

BCD tables only load in the browser

See also