Lifecycle Callbacks
Special methods called lifecycle callbacks allow you to respond whenever a controller connects to and disconnects from the document.
import { Controller } from "stimulus"
export default class extends Controller {
connect() {
// …
}
}
﹟Methods
You may define any of the following methods in your controller:
| Method | Invoked by Stimulus… |
|---|---|
| initialize() | Once, when the controller is first instantiated |
| connect() | Anytime the controller is connected to the DOM |
| disconnect() | Anytime the controller is disconnected from the DOM |
﹟Connection
A controller is connected to the document when both of the following conditions are true:
- its element is present in the document (i.e., a descendant of
document.documentElement, the<html>element) - its identifier is present in the element’s
data-controllerattribute
When a controller becomes connected, Stimulus calls its connect() method.
﹟Disconnection
A connected controller will later become disconnected when either of the preceding conditions becomes false, such as under any of the following scenarios:
- the element is explicitly removed from the document with
Node#removeChild()orChildNode#remove() - one of the element’s parent elements is removed from the document
- one of the element’s parent elements has its contents replaced by
Element#innerHTML= - the element’s
data-controllerattribute is removed or modified - the document installs a new
<body>element, such as during a Turbo page change
When a controller becomes disconnected, Stimulus calls its disconnect() method.
﹟Reconnection
A disconnected controller may become connected again at a later time.
When this happens, such as after removing the controller’s element from the document and then re-attaching it, Stimulus will reuse the element’s previous controller instance, calling its connect() method multiple times.
﹟Order and Timing
Stimulus watches the page for changes asynchronously using the DOM MutationObserver API.
This means that Stimulus calls your controller’s lifecycle methods asynchronously after changes are made to the document, in the next microtask following each change.
Lifecycle methods still run in the order they occur, so two calls to a controller’s connect() method will always be separated by one call to disconnect().