In JavaScript, a Promise is an object that represents the eventual completion or failure of an asynchronous operation. It is a way to handle asynchronous operations without getting into callback hell, which is a situation where multiple callback functions create unmanageable code. A Promise can have one of three states: pending, resolved, or rejected.
When a Promise is created, it takes a function called the executor as an argument. The executor function takes two parameters: resolve and reject. The resolve function is called when the Promise is successful, and the reject function is called when the Promise fails.
Promises can be consumed by registering functions using the then() and catch() methods. The then() method is invoked when a Promise is either resolved or rejected. It takes two functions as parameters: the first function is executed if the Promise is resolved and a result is received, and the second function is executed if the Promise is rejected and an error is received.
Here are some key points to remember about Promises in JavaScript:
- A Promise is an object that represents the eventual completion or failure of an asynchronous operation.
- A Promise can have one of three states: pending, resolved, or rejected.
- Promises can be consumed by registering functions using the then() and catch() methods.
- The then() method is invoked when a Promise is either resolved or rejected.
- The executor function is called when a Promise is created and takes two parameters: resolve and reject.
