Java Script Promise

What are Promises?

Promises are objects that represent the eventual result of an asynchronous operation (an operation that takes time to complete, like fetching data from a server).

They provide a cleaner way to handle asynchronous code compared to traditional callbacks, leading to more readable and maintainable code.

Key Concepts:

States: A Promise can be in one of three states:

Pending: The initial state, where the operation is ongoing.

Fulfilled: The operation completed successfully, and the Promise has a value.

Rejected: The operation failed, and the Promise has an error reason.

Creating Promises:

Consuming Promises:

Key Methods:

• then(): Attaches a handler to be called when the Promise is fulfilled.
• catch(): Attaches a handler to be called when the Promise is rejected.

finally(): Attaches a handler that always executes, regardless of whether the Promise is fulfilled or rejected. Benefits of Promises: Cleaner code: Improve code readability and maintainability compared to callbacks. Chaining: Promises can be chained together, allowing for sequential asynchronous operations. Error handling: Provides a structured way to handle errors using catch(). Common Use Cases:

• Fetching data from APIs
• Reading and writing files
• Handling user interactions (e.g., clicks)
• Performing complex calculations

Composing asynchronous actions


  Additional Notes: 👉Promises can be chained using then(), allowing for sequential asynchronous actions. 👉Handling multiple asynchronous operations can be simplified using Promise.all() and Promise.race(). 👉Modern JavaScript features like async/await provide syntactic sugar for working with Promises, making code even more readable.