Streaming with promises in Svelte - Cheat Sheet & Quick Revision

Recall & Review

beginner

What is a promise in JavaScript?

A promise is an object that represents the eventual completion or failure of an asynchronous operation and its resulting value.

intermediate

How does streaming with promises improve user experience in Svelte?

Streaming with promises allows parts of the UI to render as soon as data is available, making the app feel faster and more responsive.

beginner

In Svelte, how can you use a promise to show loading and then display data?

Use the {#await promise} block to show a loading state, then display the resolved data inside the then section of the {#await} block.

intermediate

What happens if a promise rejects inside a Svelte {#await} block?

You can handle errors by adding a catch block inside {#await} to show an error message or fallback UI.

beginner

Why is streaming with promises better than waiting for all data before rendering?

Streaming lets the app show parts of the UI immediately as data arrives, reducing wait time and improving perceived speed.

In Svelte, which block is used to handle promises for streaming data?

A {#await}

B {#if}

C {#each}

D {#then}

The {#await} block is designed to handle promises, showing loading, then resolved data or errors.

What does the 'then' section inside a Svelte {#await} block do?

A Shows loading state

B Handles errors

C Cancels the promise

D Displays resolved promise data

The 'then' section runs when the promise resolves successfully and displays the data.

How can you show an error message if a promise fails in Svelte?

A Use a catch block inside {#await}

B Use an else block

C Use a try-catch statement in markup

D Use a separate component

The catch block inside {#await} handles rejected promises and shows error UI.

Why is streaming with promises useful in web apps?

A It blocks user interaction

B It delays rendering until all data loads

C It allows showing UI parts as data arrives

D It caches all data locally

Streaming lets the app render parts immediately, improving user experience.

Which of these is NOT a benefit of streaming with promises?

A Faster perceived loading

B Guarantees data arrives instantly

C Immediate UI updates

D Better error handling

Streaming improves perceived speed but cannot make data arrive instantly.

Explain how you would use Svelte's {#await} block to stream data from a promise, including loading and error states.

Think about the three parts: loading, success, and error.

Describe why streaming with promises can make a web app feel faster and more responsive.

Compare waiting for all data vs showing partial data early.