Senior LevelJavaScript & TypeScript
What is top-level await, dynamic import(), and code splitting in modern JS/TS applications?
❓ Interview Prompt: Explain Top-Level Await module execution graph blocking, module dependency trees, and dynamic imports.
Top-Level Await allows the await keyword to be used outside of async functions at the top level of ES modules.
Module Execution Impact:
When a module uses top-level await, its module execution is paused until the awaited promise settles. Any child modules importing this module will wait for its resolution before executing.
Best Practice:
Use top-level await sparingly for critical asynchronous module initialization (e.g. database connection setups or dynamic language asset loading).
Code Implementation Example
javascript
// dbConnection.js (ES Module with Top-Level Await)
const connection = await fetchDbCredentials();
export const db = await connectToDatabase(connection);
// main.js (Imports dbConnection)
import { db } from './dbConnection.js';
// Execution reaches main.js ONLY after db connection promise has resolved!
db.query('SELECT * FROM users');💡Top-Level Await pausing module dependency graph execution until async setup completes.
🎯 Interview Key Takeaway
Top-level await pauses dependent module execution until the promise resolves, enabling clean module-level initialization.
#Top-Level Await#ESM#Modules#Senior
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