Thursday, 4 January 2024 • 📚 2 min read • back to Blog • edit on Github

One of the Angular 17 awesome features shipped is the defer block which allows to lazy load components, directives and pipes, while configuring it on the template level via @defer.

If you already know the theory and want to get your hands dirty with @defer, here's an app you can see various usecases and combinations:

ducin.github.io/angular-defer

See how does application runtime and user interaction trigger @defer and what certain bundles get loaded into the browser.

It includes:

• ⚡️ components, directives, pipes
• ⚡️ multiple triggers and their combinations
• ⚡️ practical usecases (🪗 accordion, 📦 npm package and many more)
• ⚡️ analyze with devtools
• ⚡️ explanations included

Usecases implemented:

• ⚡️ when condition: @defer (when isVisible) {...}
• ⚡️ on idle: @defer (on idle) {...}
• ⚡️ on viewport: @defer (on viewport) {...}
• ⚡️ on interaction: @defer (on interaction) {...}
• ⚡️ on hover: @defer (on hover) {...}
• ⚡️ on immediate: @defer (on immediate) {...}
• ⚡️ on timer: @defer (on timer(2000ms)) {...}
• 🪗 accordion: @defer (on hover(accordion); on timer(5s)) {...} (before accordion section gets clicked)
• 👫 multiple deferrable
• 📦 npm package: <link rel="modulepreload" href="chunk-BYHJVGJ4.js">
• 🗃️ nested defer: @defer (on timer(2s)) { @defer (on interaction) {...} }
• ⏱️ prefetch: @defer (on interaction; prefetch on idle) {...}
• 🚚 loading vs placeholder: placeholder (minimum 500ms) {...} & @loading (minimum 1s; after 10ms) {...}
• 💥 defer error: @error {...}

So open your browser devtools Network tab and have a play with the interactive examples 💪

---