Understanding Promises
Promises are a modern feature in Node.js that help you manage asynchronous operations more effectively. A Promise represents a value that may be available now, in the future, or never. Promises have three possible states:
- Pending - the initial state, before the operation completes;
- Fulfilled - the operation completed successfully;
- Rejected - the operation failed.
You can attach handlers to a Promise to run code when it is fulfilled or rejected, and you can chain multiple asynchronous operations together for clearer, more manageable code.
index.js
Promises greatly improve the structure of asynchronous code compared to traditional callbacks. With callbacks, you often end up nesting functions inside each other, leading to code that is hard to read and maintain—a situation known as callback hell.
Promises solve this by allowing you to chain operations using then() for success and catch() for errors. This chaining makes it easier to follow the flow of asynchronous tasks and handle errors in one place, resulting in cleaner and more predictable code.
You can chain multiple asynchronous operations with Promises:
fetchData()
.then((data) => processData(data))
.then((result) => saveResult(result))
.catch((err) => console.error(err));
This ensures each step runs only after the previous one finishes, with all errors handled in a single catch block.
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Can you show me an example of how to use Promises in Node.js?
What is the difference between Promises and async/await?
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Promises are a modern feature in Node.js that help you manage asynchronous operations more effectively. A Promise represents a value that may be available now, in the future, or never. Promises have three possible states:
- Pending - the initial state, before the operation completes;
- Fulfilled - the operation completed successfully;
- Rejected - the operation failed.
You can attach handlers to a Promise to run code when it is fulfilled or rejected, and you can chain multiple asynchronous operations together for clearer, more manageable code.
index.js
Promises greatly improve the structure of asynchronous code compared to traditional callbacks. With callbacks, you often end up nesting functions inside each other, leading to code that is hard to read and maintain—a situation known as callback hell.
Promises solve this by allowing you to chain operations using then() for success and catch() for errors. This chaining makes it easier to follow the flow of asynchronous tasks and handle errors in one place, resulting in cleaner and more predictable code.
You can chain multiple asynchronous operations with Promises:
fetchData()
.then((data) => processData(data))
.then((result) => saveResult(result))
.catch((err) => console.error(err));
This ensures each step runs only after the previous one finishes, with all errors handled in a single catch block.
Grazie per i tuoi commenti!
