Asynchronous Operations with Promises and Async/Await

Proper handling of asynchronous operations is essential for modern JavaScript development, especially when handling I/O operations such as network requests or accessing files Promise and async/await provide powerful tools for checking this asynchronous code on.

 

Promises

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

Creating a Promise

Let's create a simple promise in JavaScript,

Syntax-

let promise = new Promise((resolve, reject) => {
   // Asynchronous operation
   if (success) {
       resolve(value); // On success
   } else {
       reject(error); // On failure
   }
});

Example-

let promise = new Promise((resolve, reject) => {
   setTimeout(() => {
       resolve("Operation successful");
   }, 1000);
});
promise.then((result) => {
   console.log(result); // "If Operation successful"
}).catch((error) => {
   console.error(error); // "If Operation failed"
});

Chaining Promises

let promise = new Promise((resolve, reject) => {
   setTimeout(() => resolve(1), 1000);
});
promise
   .then(result => {
       console.log(result); // 1
       return result * 2;
   })
   .then(result => {
       console.log(result); // 2
       return result * 2;
   })
   .then(result => {
       console.log(result); // 4
   })
   .catch(error => {
       console.error(error);
   });

 

async/wait

async/await is a syntax sugar built on top of Promises, providing a straightforward way to execute asynchronous code.

Using async Functions

async function functionName() {
   // Asynchronous code
   let result = await promise;
   // Process result
}

Example- 

async function fetchData() {
   try {
       let response = await fetch("https://api.example.com/data");
       let data = await response.json();
       console.log(data);
   } catch (error) {
       console.error("Error fetching data:", error);
   }
}
fetchData();

Error Handling in async/await

async function riskyOperation() {
   try {
       let result = await someAsyncFunction();
       console.log(result);
   } catch (error) {
       console.error("Error during risky operation:", error);
   }
}
riskyOperation();

 

Combining promise and async/wait

You can mix Promises and have async/await flexibility and handle asynchronous operations.

Example- 

async function fetchData(url) {
   let response = await fetch(url);
   if (!response.ok) {
       throw new Error("Network response was not ok");
   }
   return response.json();
}
function logData(url) {
   fetchData(url)
       .then(data => console.log(data))
       .catch(error => console.error("Error fetching data:", error));
}
logData("https://api.example.com/data");

 

Best Practices

Always handle errors- use catch for promises and try…catch for async/await to handle errors.
Use async/await for readability- When handling a lot of asynchronous operations, async/await tends to result in cleaner and more readable code.
Avoid Mixing- want to use Promises or async/await in a given piece of code for clarity.
Graceful Degradation- Make sure your code can handle failures gracefully, providing fallback options or user notifications.

With proper use of Promises and async/await, you can manage asynchronous functions more effectively in JavaScript, resulting in more maintainable and reliable code.

 

Also, Read: Error Handling in JavaScript