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What are promises and what is the difference between Promise.all, Promise.allSettled, Promise.race and Promise.any?
Introduction
Promises in JavaScript are used to handle asynchronous operations by keeping track of whether a certain event has happened. If that certain event has taken place, it determines what happens next. Promises return a value which is either a resolved value or a reason why it’s rejected. They can handle multiple asynchronous operations easily and they provide better error handling than callbacks and events.
Callback: A callback is a function that is passed into another function as an argument to be executed later.
Events: Events provide a dynamic interface to a WebPage and are connected to elements in the Document Object Model(DOM), for example: onclick(), onmouseover() etc.
A Promise has four states
Pending: Before the event has happened, the promise is in the pending state.
Settled: Once the event has happened it is then in the settled state.
Fulfilled: Action related to the promise has succeeded.
Rejected: Action related to the promise has failed.
An example of a Promise that resolves successfully:
An example of a rejected promise:
Comparison Table
Promise.all()
The Promise.all() method executes many promises in parallel. It accepts an array of promises and returns a single…
