PageLifecycle.js
Overview
PageLifecycle.js is a tiny JavaScript library (<1K gzipped) that allows developers to easily observe Page Lifecycle API state changes and implement Page Lifecycle best practices consistently across all browsers.
Installation
You can install this library from npm by running:
npm install --save-dev page-lifecycle
Usage
Releases of this library include three minified, production-ready versions:
1. ES5: dist/lifecycle.es5.js
(UMD)
Use this version for maximum compatibility with legacy browsers (that can't run ES2015+ code).
As a UMD bundle, it can be required in CommonJS or AMD environments, or it can be loaded with a script tag as the browser global lifecycle
.
<script defer src="/path/to/lifecycle.es5.js"></script>
<script defer>
lifecycle.addEventListener('statechange', function(event) {
console.log(event.oldState, event.newState);
});
</script>
2. ES2015: dist/lifecycle.mjs
(ESM)
Use this version if you only support ES module-capable browsers or if you're using <script type="module">
and the nomodule
fallback to conditionally target modern browsers.
<script type="module">
import lifecycle from '/path/to/page-lifecycle.mjs';
lifecycle.addEventListener('statechange', function(event) {
console.log(event.oldState, event.newState);
});
</script>
3. ES2015 (native): dist/lifecycle.native.mjs
(ESM w/o EventTarget
and Event
shims)
Use this version if you're only targeting browsers that support extending EventTarget
and Event
constructors.
Note: this version is the smallest but will only work in some browsers. The implementation instructions are the same as the ES2015 version above.
API
The PageLifecycle.js library exports a lifecycle
object, which is a singleton instance of the Lifecycle
class. The Lifecycle
class has the following properties, methods, and events:
Properties
Name | Type | Description |
---|---|---|
state |
string |
Returns the current Page Lifecycle state. |
pageWasDiscarded |
boolean |
Returns the value of document.wasDiscarded (or false if not present).
|
Methods
Name | Description |
---|---|
addEventListener |
Parameters:
Adds a callback function to be invoked whenever the passed event type is detected. (Note: at the moment only the "statechange" event type is supported.) |
removeEventListener |
Parameters:
Removes a function from the current list of listeners for the passed event type. (Note: at the moment only the "statechange" event type is supported.) |
addUnsavedChanges |
Parameters:
Adds an item to an internal pending-changes stack. Calling this method adds a generic The argument passed should be unique to this state, as it can only be removed by passing the same argument to |
removeUnsavedChanges |
Parameters:
Removes an item matching the passed argument from an internal pending-changes stack. If the stack is empty, the generic |
Events
Name | Description |
---|---|
statechange |
Properties:
The |
Browser Support
|
|
|
|
9+ |
|
PageLifecycle.js has been tested and known to work in the above browsers.