The popstate
event of the Window
interface is fired when the active history entry changes while the user navigates the session history. It changes the current history entry to that of the last page the user visited or, if history.pushState()
has been used to add a history entry to the history stack, that history entry is used instead.
Syntax
Use the event name in methods like addEventListener()
, or set an event handler property.
addEventListener("popstate", (event) => {});
onpopstate = (event) => {};
Event type
Event properties
-
PopStateEvent.state
Read only
-
Returns a copy of the information that was provided to pushState()
or replaceState()
.
Event handler aliases
In addition to the Window
interface, the event handler property onpopstate
is also available on the following elements:
The history stack
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.
These methods and their corresponding events can be used to add data to the history stack which can be used to reconstruct a dynamically generated page, or to otherwise alter the state of the content being presented while remaining on the same Document
.
Note that just calling history.pushState()
or history.replaceState()
won't trigger a popstate
event. The popstate
event will be triggered by doing a browser action such as a click on the back or forward button (or calling history.back()
or history.forward()
in JavaScript).
Browsers tend to handle the popstate
event differently on page load. Chrome (prior to v34) and Safari always emit a popstate
event on page load, but Firefox doesn't.
Note: When writing functions that process popstate
event it is important to take into account that properties like window.location
will already reflect the state change (if it affected the current URL), but document
might still not. If the goal is to catch the moment when the new document state is already fully in place, a zero-delay setTimeout()
method call should be used to effectively put its inner callback function that does the processing at the end of the browser event loop: window.onpopstate = () => setTimeout(doSomeThing, 0);
When popstate is sent
It's important to first understand that — to combat unwanted pop-ups — browsers may not fire the popstate
event at all unless the page has been interacted with.
This section describes the steps that browsers follow in the cases where they do potentially fire the popstate
event (that is, in the cases where the page has been interacted with).
When a navigation occurs — either due to the user triggering the browser's Back button or otherwise — the popstate
event is near the end of the process to navigate to the new location. It happens after the new location has loaded (if needed), displayed, made visible, and so on — after the pageshow
event is sent, but before the persisted user state information is restored and the hashchange
event is sent.
To better understand when the popstate
event is fired, consider this simplified sequence of events that occurs when the current history entry changes due to either the user navigating the site or the history being traversed programmatically. Here, the transition is changing the current history entry to one we'll refer to as new-entry. The current page's session history stack entry will be referred to as current-entry.
- If new-entry doesn't currently contain an existing
Document
, fetch the content and create its Document
before continuing. This will eventually send events such as DOMContentLoaded
and load
to the Window
containing the document, but the steps below will continue to execute in the meantime. - If current-entry's title wasn't set using one of the History API methods (
pushState()
or replaceState()
), set the entry's title to the string returned by its document.title
attribute. - If the browser has state information it wishes to store with the current-entry before navigating away from it, it then does so. The entry is now said to have "persisted user state." This information the browser might add to the history session entry may include, for instance, the document's scroll position, the values of form inputs, and other such data.
- If new-entry has a different
Document
object than current-entry, the browsing context is updated so that its document
property refers to the document referred to by new-entry, and the context's name is updated to match the context name of the now-current document. - Each form control within new-entry's
Document
that has autocomplete
configured with its autofill field name set to off
is reset. See The HTML autocomplete attribute for more about the autocomplete field names and how autocomplete works. - If new-entry's document is already fully loaded and ready—that is, its
readyState
is complete
—and the document is not already visible, it's made visible and the pageshow
event is fired at the document with the PageTransitionEvent
's persisted
attribute set to true
. - The document's
URL
is set to that of new-entry. - If the history traversal is being performed with replacement enabled, the entry immediately prior to the destination entry (taking into account the
delta
parameter on methods such as go()
) is removed from the history stack. - If the new-entry doesn't have persisted user state and its URL's fragment is non-
null
, the document is scrolled to that fragment. - Next, current-entry is set to new-entry. The destination entry is now considered to be current.
- If new-entry has serialized state information saved with it, that information is deserialized into
History.state
; otherwise, state
is null
. - If the value of
state
changed, the popstate
event is sent to the document. - Any persisted user state is restored, if the browser chooses to do so.
- If the original and new entries shared the same document, but had different fragments in their URLs, send the
hashchange
event to the window.
As you can see, the popstate
event is nearly the last thing done in the process of navigating pages in this way.
Examples
A page at http://example.com/example.html
running the following code will generate logs as indicated:
window.addEventListener("popstate", (event) => {
console.log(
`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();
history.back();
history.go(2);
The same example using the onpopstate
event handler property:
window.onpopstate = (event) => {
console.log(
`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();
history.back();
history.go(2);
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
Browser compatibility
|
Desktop |
Mobile |
|
Chrome |
Edge |
Firefox |
Internet Explorer |
Opera |
Safari |
WebView Android |
Chrome Android |
Firefox for Android |
Opera Android |
Safari on IOS |
Samsung Internet |
popstate_event |
5Before version 34, Chrome would fire a popstate event on page load. |
12 |
4 |
10 |
11.5 |
5Before version 10, Safari would fire a popstate event on page load. |
≤37Before version 37, WebView would fire a popstate event on page load. |
18Before version 34, Chrome would fire a popstate event on page load. |
4 |
11.5 |
4.2Before version 10, Safari would fire a popstate event on page load. |
1.0Before version 2.0, Samsung Internet would fire a popstate event on page load. |
See also