Event Bubbling

In plain words: In Lightning Web Components (LWC) , components communicate upwards by creating and dispatching a CustomEvent . A child component fires the event with a data payload, and an ancestor component catches it using an on{eventname} declarative listener or a programmatic DOM listener. Building maintainable Salesforce applications requires clean component communication. LWC adheres to standard DOM events following the principle of "properties down, events up." Below are three complete code patterns demonstrating direct child-to-parent messaging, cross-boundary event bubbling, and stopping event propagation.