Explain Promise in JavaScript?

A promise is an object in JavaScript which is used to produce a value that may give results in the future. The value can be resolved value or it can be a reason which tells why the value is not resolved.

A promise can be of three states:

• Fulfilled: The operation is completed and the promise has a specific value.
• Rejected: The operation is failed and promise has a reason which shows why the operation failed.
• Pending: Th operation is not fulfilled or rejected, which means it has not completed yet.