wtf is request-idle-callback?

This project provides a tool for Angular developers to schedule background tasks during moments when the browser isn't busy. Think of it like telling your app: "Hey, when you have a free moment and the user isn't doing anything, go ahead and load this extra data or process this non-urgent task." The browser is constantly doing work, rendering animations, responding to clicks, updating the screen. If you try to do extra work at the wrong time, it can make the app feel slow or janky. requestIdleCallback is a browser feature that helps you find those tiny gaps of free time between frames where you can safely do work without slowing things down. This library makes it easy to use that feature in Angular apps, and it works across different platforms including server-side rendered apps (where the browser APIs aren't available). A concrete example: imagine you've built a web app and after the user logs in, you want to prefetch data for pages they might visit next. Instead of loading that data immediately (which would delay the login experience), you could schedule it to load when the browser is idle, maybe a second after the user sees the main screen. The library lets you do this with just a few lines of code, either by calling requestIdleCallback directly in your components or by passing an array of callback functions to run during idle time. This is most valuable for Progressive Web Apps and universal Angular apps (apps that run on both server and browser), where performance matters and you want to make sure you're not blocking user interactions. The README emphasizes that trying to figure out idle time manually is nearly impossible, you'd have to listen for clicks, scrolls, touches, and guess at frame timing. The browser already knows when it's truly idle, so it's much smarter to let it handle the scheduling for you.