Four advanced JavaScript techniques could surprise you in your next interview. Let’s keep it short and sweet with just the key points and code examples.

1. Top-Level Await

// Fetching data at the module level
const response = await fetch('https://api.example.com/data');
const data = await response.json();

export default data;

Key Point: Simplifies async operations in modules.

Example: Imagine you need to fetch configuration settings from an API before initializing your app. Top-Level Await makes this straightforward without wrapping everything in async functions.

2. Temporal API (Stage 3 Proposal)

import { Temporal } from '@js-temporal/polyfill';

// Get current date and time
const now = Temporal.Now.plainDateTimeISO();
console.log(now.toString()); // 2024-08-12T10:00:00

Key Point: Better handling of dates/times than Date object.

Example: Working on a global app? The Temporal API allows you to accurately handle time zones, avoiding the pitfalls of the Date object.

3. Pattern Matching (Stage 3 Proposal)

const value = { x: 1, y: 2 };
const result = match (value) {
  {x: 1, y: 2} => 'Point at (1, 2)',
  {x, y} if (x > y) => 'X is greater',
  _ => 'Unknown pattern'
};
console.log(result);

Key Point: Powerful alternative to switch statements.

Example: Simplify complex conditional logic in data processing by matching patterns directly, reducing the need for nested if-else statements.

4. Records and Tuples (Stage 2 Proposal)

const record = #{ x: 1, y: 2 };
const tuple = #[1, 2, 3];

console.log(record.x); // 1
console.log(tuple[0]); // 1

Key Point: Immutable data structures for safer code.

Example: Use Records and Tuples to ensure that critical data structures remain unchanged throughout your application, preventing unintended mutations.

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