Marks class as having finished creating properties.
User-supplied object that maps property names to PropertyDeclaration
objects containing options for configuring the property.
Returns a Promise that resolves when the element has completed updating.
The Promise value is a boolean that is true if the element completed the
update without triggering another update. The Promise result is false if
a property was set inside updated(). If the Promise is rejected, an
exception was thrown during the update.
To await additional asynchronous work, override the _getUpdateComplete
method. For example, it is sometimes useful to await a rendered element
before fulfilling this Promise. To do this, first await
super._getUpdateComplete(), then any subsequent state.
The Promise returns a boolean that indicates if the update resolved without triggering another update.
Returns a list of attributes corresponding to the registered properties.
Override point for the updateComplete promise.
It is not safe to override the updateComplete getter directly due to a
limitation in TypeScript which means it is not possible to call a
superclass getter (e.g. super.updateComplete.then(...)) when the target
language is ES5 (https://github.com/microsoft/TypeScript/issues/338).
This method should be overridden instead. For example:
class MyElement extends LitElement { async getUpdateComplete() { await super.getUpdateComplete(); await this._myChild.updateComplete; } }
Synchronizes property values when attributes change.
Allows for super.disconnectedCallback() in extensions while
reserving the possibility of making non-breaking feature additions
when disconnecting at some point in the future.
Invoked when the element is first updated. Implement to perform one time work on the element after update.
Setting properties inside this method will trigger the element to update again after this update cycle completes.
Map of changed properties with old values
Performs element initialization. By default captures any pre-set values for registered properties.
Performs an element update. Note, if an exception is thrown during the
update, firstUpdated and updated will not be called.
You can override this method to change the timing of updates. If this
method is overridden, super.performUpdate() must be called.
For instance, to schedule updates to occur just before the next frame:
protected async performUpdate(): Promise<unknown> {
await new Promise((resolve) => requestAnimationFrame(() => resolve()));
super.performUpdate();
}Requests an update which is processed asynchronously. This should
be called when an element should update based on some state not triggered
by setting a property. In this case, pass no arguments. It should also be
called when manually implementing a property setter. In this case, pass the
property name and oldValue to ensure that any configured property
options are honored. Returns the updateComplete Promise which is resolved
when the update completes.
(optional) name of requesting property
(optional) old value of requesting property
A Promise that is resolved when the update completes.
Controls whether or not update should be called when the element requests
an update. By default, this method always returns true, but this can be
customized to control when to update.
Map of changed properties with old values
Updates the element. This method reflects property values to attributes. It can be overridden to render and keep updated element DOM. Setting properties inside this method will not trigger another update.
Map of changed properties with old values
Invoked whenever the element is updated. Implement to perform post-updating tasks via DOM APIs, for example, focusing an element.
Setting properties inside this method will trigger the element to update again after this update cycle completes.
Map of changed properties with old values
Creates a property accessor on the element prototype if one does not exist.
The property setter calls the property's hasChanged property option
or uses a strict identity check to determine whether or not to request
an update.
Creates property accessors for registered properties and ensures any superclasses are also finalized.
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Base element class which manages element properties and attributes. When properties change, the
updatemethod is asynchronously called. This method should be supplied by subclassers to render updates as desired.