[enhancement] Add discard-on-disconnect boolean attribute to clean up the element
Backgrounds
Disconnected custom elements are still active and working
Some iterated elements should be discarded after disconnection
The element must be cleaned up on discarding
Features
Add discard-on-disconnect boolean attribute to perform cleaning-up on disconnect
Tasks in disconnectedCallback()
Call super.disconnectedCallback() if exists
Clean up lang-updated event listener _updateEffectiveLang()
Clean up lang-updated event listeners on boundElement associated to this
Disconnect the mutation observer for <html lang> attribute
Notes
The element's disconnectedCallback must call super.disconnectedCallback() and perform its specific cleanup tasks
Memory profiler shows that elements with discard-on-disconnect attributes are garbage collected on disconnection while element without the attributes are not garbage collected
For world-clock element in the demo, it is unnecessary to empty their shadowRoot for garbage collection.
In some cases, it should be required for an element to clean up this.shadowRoot by this.shadowRoot.innerHTML = '' on disconnection to get itself garbage collected.
[enhancement] Add
discard-on-disconnectboolean attribute to clean up the elementBackgrounds
Features
discard-on-disconnectboolean attribute to perform cleaning-up on disconnectdisconnectedCallback()super.disconnectedCallback()if existslang-updatedevent listener_updateEffectiveLang()lang-updatedevent listeners onboundElementassociated tothis<html lang>attributeNotes
disconnectedCallbackmust callsuper.disconnectedCallback()and perform its specific cleanup tasksdiscard-on-disconnectattributes are garbage collected on disconnection while element without the attributes are not garbage collectedworld-clockelement in the demo, it is unnecessary to empty theirshadowRootfor garbage collection.this.shadowRootbythis.shadowRoot.innerHTML = ''on disconnection to get itself garbage collected.