Here are the key features introduced in ES8 (ECMAScript 2017), with detailed descriptions and examples:

1. Async/Await:

• Simplifies asynchronous code handling by making it look more like synchronous code, improving readability and maintainability.
• Key components:
  • async keyword for marking asynchronous functions.
  • await keyword for pausing execution within async functions until a Promise is resolved/rejected.

JavaScript

async function fetchData() {
  try {
    const response = await fetch('https://api.example.com/data');
    const data = await response.json();
    console.log(data);
  } catch (error) {
    console.error(error);
  }
}

2. Shared Memory and Atomics:

• Enables communication between threads in web workers using shared memory and atomic operations for synchronization.
• Use cases: Parallel processing, performance optimization.

JavaScript

// Worker thread:
const sharedArray = new SharedArrayBuffer(16);
const view = new Int32Array(sharedArray);
view[0] = 42; // Write to shared memory

// Main thread:
const receivedValue = view[0]; // Access shared memory

3. Object.values/Object.entries:

• Return arrays of object values or key-value pairs:
  • Object.values(obj) returns an array of object’s own enumerable property values.
  • Object.entries(obj) returns an array of key-value pairs as arrays.

JavaScript

const person = { name: "John", age: 30 };
const values = Object.values(person); // ["John", 30]
const entries = Object.entries(person); // [["name", "John"], ["age", 30]]

4. String Padding:

• Pads strings with spaces or specified characters:
  • padStart(targetLength, padString) pads the beginning.
  • padEnd(targetLength, padString) pads the end.

JavaScript

const paddedNumber = "123".padStart(5, "0"); // "00123"
const paddedName = "Alice".padEnd(10, " "); // "Alice     "

5. Trailing Commas in Function Parameter Lists and Calls:

• Allows trailing commas in function parameter lists and calls for better formatting and version control.

JavaScript

function myFunction(a, b, c,) { // Trailing comma allowed
  // ...
}

myFunction(1, 2, 3,); // Trailing comma allowed