The second call to resolve is ignored, because only the first call of reject/resolve is taken into account. To get some relief, you promise to send it to them when it’s published. We can use the methods .then/.catch/.finally for that. Promises allow you to attach callback handlers to handle the future asynchronous success value or failure reason. Subscriptions in real life must be done prior to the event. In JavaScript, a promise is an object that represents an asynchronous operation. We also can call resolve or reject immediately, like this: For instance, this might happen when we start to do a job but then see that everything has already been completed and cached. Promise.then() takes two arguments, a callback for success and another for failure. A good way to think about JavaScript promises is to compare them to how people make promises. Do something within the callback, perhaps async, then call resolve if everything worked, otherwise call reject. When it comes to JavaScript, a promise that is fulfilled is said to be resolved while that that is broken is said to be rejected. In finally we don’t know whether the promise is successful or not. The outer code can add handlers (subscribing functions) to it using .then: We can immediately see a few benefits over the callback-based pattern: So promises give us better code flow and flexibility. We’ll talk more about promise chaining and result-passing between handlers in the next chapter. Imagine that you’re a top singer, and fans ask day and night for your upcoming single. Or we can use .catch(errorHandlingFunction), which is exactly the same: The call .catch(f) is a complete analog of .then(null, f), it’s just a shorthand. You give your fans a list. Like throw in plain old JavaScript, it's customary, but not required, to reject with an Error object. The reasoning for that will soon become apparent. Consuming functions can be registered (subscribed) using methods .then, .catch and .finally. Today’s video will cover what are promise in JavaScript and a bit about the different states of Promises. This changes the state of the promise object: That was an example of a successful job completion, a “fulfilled promise”. So first let us look at promises in real life. Prior to promises events and callback functions were used but they had limited functionalities and created unmanageable code. They can fill in their email addresses, so that when the song becomes available, all subscribed parties instantly receive it. Promises are challenging for many web developers, even after spending years working with them. We want to make this open-source project available for people all around the world. That’s all right, as our task is usually to perform “general” finalizing procedures. When a Promise object is "fulfilled", the result is a value. So what are promises? You cannot access the Promise properties state and result. This is a real-life analogy for things we often have in programming: The analogy isn’t terribly accurate, because JavaScript promises are more complex than a simple subscription list: they have additional features and limitations. Promise users can attach callbacks to handle the fulfilled value or the reason for rejection. Ein solcher Vorgang wird durch Funktion eingeleitet, die der Promise-Konstruktor als Parameter erhält. ES6 came with many new features, but one of the best features was the official introduction of Promises. Das Promise-Objekt (dt./deutsch Ein Versprechens-Objekt, das später eingelöst wird)wird für asynchrone Berechnungen verwendet. Can achieve results from performing asynchronous operations that when the request completes and a response com… now here the! A promise zu steuern und zu koordinieren similar to the next chapters argument just! 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