What Is a Promise?
JavaScript Promises are a core feature for handling asynchronous operations in a more manageable and predictable way. A Promise represents a value that may be available now, in the future, or never. Promises were introduced to solve the problems caused by deeply nested callbacks, often called callback hell, and to provide a cleaner way to work with asynchronous code.
A Promise can be in one of three distinct states:
- Pending: the initial state, before the operation has completed;
- Fulfilled: the operation completed successfully and the Promise has a resulting value;
- Rejected: the operation failed, and the Promise has a reason for the failure.
Once a Promise is fulfilled or rejected, its state cannot change again. This immutability is what makes Promises reliable for managing asynchronous flows. The introduction of Promises has made it much easier to write code that is both readable and robust when dealing with operations like network requests, timers, or reading files.
Promises help manage asynchronous operations and avoid callback hell.
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Can you give an example of how to create and use a Promise in JavaScript?
What are the main advantages of using Promises over callbacks?
How do you handle errors when working with Promises?
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JavaScript Promises are a core feature for handling asynchronous operations in a more manageable and predictable way. A Promise represents a value that may be available now, in the future, or never. Promises were introduced to solve the problems caused by deeply nested callbacks, often called callback hell, and to provide a cleaner way to work with asynchronous code.
A Promise can be in one of three distinct states:
- Pending: the initial state, before the operation has completed;
- Fulfilled: the operation completed successfully and the Promise has a resulting value;
- Rejected: the operation failed, and the Promise has a reason for the failure.
Once a Promise is fulfilled or rejected, its state cannot change again. This immutability is what makes Promises reliable for managing asynchronous flows. The introduction of Promises has made it much easier to write code that is both readable and robust when dealing with operations like network requests, timers, or reading files.
Promises help manage asynchronous operations and avoid callback hell.
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