What Are the Methods for Handling Asynchronous Operations in ES6?

In ES6 (ECMAScript 2015) and subsequent versions, various approaches for handling asynchronous operations have been introduced. These methods enhance code readability, maintainability, and make asynchronous logic handling more intuitive. Below are several primary asynchronous handling methods:

1. Promises

ES6 officially introduced the Promise object, which is a fundamental method for managing asynchronous operations. A Promise represents the eventual completion (or failure) of an asynchronous operation and its resulting value. Promise has three states: pending (pending), fulfilled (fulfilled), and rejected (rejected).

Example:

javascript
const myPromise = new Promise((resolve, reject) => {
  setTimeout(() => {
    resolve('Data retrieved');
  }, 2000);
});

myPromise.then(
  (value) => { console.log(value); },      // Success handler
  (error) => { console.error(error); }     // Error handler
);

2. Generators

Although Generator functions in ES6 are not inherently asynchronous, they can be used to control the flow of asynchronous calls. Generator functions enable pausing and resuming function execution during operation, allowing you to suspend execution while waiting for asynchronous results.

Example:

javascript
function* generatorFunction() {
  const result = yield myPromise;
  console.log(result);
}

// Using generators to manage asynchronous flow
const iterator = generatorFunction();
const prom = iterator.next().value; // Get Promise returned by yield

prom.then((response) => iterator.next(response));

3. Async/Await

async/await was introduced in ES7 (ECMAScript 2017) and builds upon ES6's Promise. It is syntactic sugar for using Promise in a more concise and readable manner. Any function marked with async returns a Promise. The await keyword pauses function execution until a Promise resolves or rejects, enabling straightforward handling of asynchronous operations.

Example:

javascript
async function fetchData() {
  try {
    const response = await fetch('https://api.example.com/data'); // Wait for Promise to resolve
    const data = await response.json(); // Wait for Promise to resolve
    console.log(data);
  } catch (error) {
    console.error('Request failed:', error);
  }
}

fetchData();

Each method has specific use cases and applicable scenarios. Promise effectively handles single or multiple asynchronous operation chains. When pausing and resuming function execution during asynchronous operations, Generator functions help manage complex workflows. async/await provides a more intuitive and concise way to handle Promise, especially when waiting for multiple asynchronous operations to complete, significantly improving code readability and maintainability.