Smart Checkbox Sync for OutSystems (Select-All With Safe Header Sync)
A lightweight JavaScript utility that provides safe and reliable checkbox synchronization between a header checkbox (Select All) and multiple item checkboxes, fully compatible with OutSystems Reactive.

Unlike typical checkbox scripts, this solution is designed specifically for OutSystems' rendering behavior, ensuring that:

• ? Local Variables are updated only via real click events

• ? “Select All” works consistently even inside Lists / TableRecords

• ? Unchecking a single item only unchecks the header (NOT all items)

• ? No infinite loops / no double-event binding

• ? Fully resistant to AJAX Refresh and DOM re-rendering

• ? Uses MutationObserver to re-bind automatically when OutSystems refreshes content