Before promises, in order to handle asynchronous requests callback function were used. But there are limitations with callbacks. Promises overcomes those limitations.
A promise is an object which handles asynchronous requests. When the implementation is correct, it will always promise that you will get a single response (either success or error) in the future. With the help of promise, you can manage asynchronous requests in a clean way as compare to callback functions.
Promise can be in any of the three states. These states are Pending, Fulfilled or Rejected. Through its entire life-cycle it can be in only two states, first will be Pending state and second will be either Fulfill or Reject state. …