In Web development, it's all about operating data when some event happens like, form submit, button clicked, mouse hover but when it comes to handling event's with react, react do it slightly differently. Your event handlers will be passed instances of SyntheticEvent, a cross-browser wrapper around the browser’s native event. It has the same interface as the browser’s native event, including stopPropagation() and preventDefault(), except the events work identically across all browsers.
Reducers are not new to react as it all started with redux and community loved it so much that react team build out an entire hook based on this pattern.
With each passing day, we see many new frontend libraries coming into practices. All major frontend development started with JQuery and today we are here, where we have React, Angular, Vue, Ember etc. and all these libraries have few things in common, that they all operate on component level. In every other frontend framework we have different option to create application but the underlying principle is using components only.