Window: pageshow event

The pageshow event is sent to a Window when the browser displays the window's document due to navigation.

This includes:

  • Initially loading the page
  • Navigating to the page from another page in the same window or tab
  • Restoring a frozen page on mobile OSes
  • Returning to the page using the browser's forward or back buttons

Note: During the initial page load, the pageshow event fires after the load event.？？

Syntax

Use the event name in methods like addEventListener(), or set an event handler property.

js
addEventListener("pageshow", (event) => {});
onpageshow = (event) => {};

Event type

A PageTransitionEvent. Inherits from Event.

Event PageTransitionEvent

Event properties

PageTransitionEvent.persisted Read only

Indicates if the document is loading from a cache.  -- 是bfcache，而不是指 network cache！

Event handler aliases

In addition to the Window interface, the event handler property onpageshow is also available on the following targets:

Examples

This example sets up event handlers for events listed in the array events. The handler, eventLogger(), logs the type of event that occurred to the console, and includes the value of the persisted flag on pageshow and pagehide events.

这个例子有问题，加入了 unload 事件，则 persisted 总是返回 false

JavaScript

js
const events = ["pagehide", "pageshow", "unload", "load"];

const eventLogger = (event) => {
  switch (event.type) {
    case "pagehide":
    case "pageshow": {
      let isPersisted = event.persisted ? "persisted" : "not persisted";
      console.log(`Event: ${event.type} - ${isPersisted}`);
      break;
    }
    default:
      console.log(`Event: ${event.type}`);
      break;
  }
};

events.forEach((eventName) => window.addEventListener(eventName, eventLogger));

HTML

html
<p>
  Open the console and watch the output as you navigate to and from this page.
  Try loading new pages into this tab, then navigating forward and backward
  through history, noting the events' output to the log.
</p>

Results

Specifications

Specification
HTML Standard
# event-pageshow

Browser compatibility

BCD tables only load in the browser

See also