javascript promise then
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success () and error () are only available on the jqXHR object returned by a call to ajax (). Eine Function, welche aufgerufen wird, wenn der Promise erfüllt wurde. If you haven’t already created an account, you will be prompted to do so after signing in.
The whole thing works, because a call to promise.then returns a promise, so that we can call the next .then on it. Although, as I mentioned, jQuery's Deferreds are a bit … unhelpful. The source for this interactive demo is stored in a GitHub repository. Das Promise-Objekt (dt./deutsch Ein Versprechens-Objekt, das später eingelöst wird)wird für asynchrone Berechnungen verwendet. Callbacks added with .then even afterthe success or failure of the asynchronous operation, will be called, as above. JavaScript Promise then() is an inbuilt function that returns a Promise. The then() method takes up to two arguments: callback functionsfor the success and failure cases of the Promise. Um mehr darüber zu erfahren wie promises funktionieren und wie diese verwendet werden sollte zuerst Dieses kleine Beispiel zeigt den Mechanismus eines Dieses Beispiel wird ausgeführt, wenn der Button geklickt wird. Multiple callbacks may be added by calling .then several times, to be executed independently in insertion order. Promises in JavaScriptare an object representation of an asynchronous computation. When a handler returns a value, it becomes the result of that promise, so the next .then is called with it. The below snippet simulates asynchronous code with the setTimeout function.
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2. fulfilled(erfüllt): heisst das die Operation erfolgreich abgeschlossen wurde.
The then method returns a Promise which allows for method chaining.If the function passed as handler to then returns a Promise, an equivalent Promise will be exposed to the subsequent then in the method chain. promise.then(doneCallback, failCallback) // was equivalent to promise.done(doneCallback).fail(failCallback) As of 1.8, then () is an alias for pipe () and returns a new promise, see here for more information on pipe ().
Eine Function, welche aufgerufen wird, wenn der Promise fehlschlägt. Thankfully you can cast them to standard promises, which is worth doing as soon as possible:
Ein weiterer Begriff beschreibt den Zustand settled (erledigt aber nicht zwingend erfolgr… Wenn Sie noch kein Konto erstellt haben, werden Sie nach der Anmeldung dazu aufgefordert. Die Funktio… Callbacks will never be called before the completion of the current runof the JavaScript event loop.
3. The JavaScript promises API will treat anything with a then() method as promise-like (or thenable in promise-speak sigh), so if you use a library that returns a Q promise, that's fine, it'll play nice with the new JavaScript promises.
Die Funktion hat ein Argument, den Rückgabewert value. Man benötigt einen Browser, der Ein weiteres, einfaches Beispiel für die Verwendung von Promises und [1] Gecko 24 hat eine experimentelle Implementierung von Erhalten Sie das Neueste und Wichtigste von MDN direkt in Ihren Posteingang.Der Newsletter wird derzeit nur auf Englisch angeboten. 2. Ein Promisekann sich in einem von drei Zuständen befinden: 1. pending(schwebend): initialer Status, weder fulfilled noch rejected. onRejected Optional 1. Unlike old-style passed-in callbacks, a promise comes with some guarantees: 1. onFulfilled 1. Basically, we reduce an array of asynchronous functions down to a promise chain equivalent to: Promise.resolve().then(func1).then(func2).then(func3); This can be made into a reusable compose function, which is common in functional programming:
If you'd like to contribute to the interactive demo project, please clone If one or both arguments are omitted or are provided non-functions, then Following, an example to demonstrate the asynchronicity of the In all other cases, a resolving Promise is returned. 3. rejected(zurück gewiesen): heisst das die Operation gescheitert ist. But the most immediate benefit of promises is chaining.
A classic newbie error: technically we can also add many .then to a single promise… In the following example, the first In practice, it is often desirable to catch rejected promises rather than use You can also use chaining to implement one function with a Promise-based API on top of another such function.Get the latest and greatest from MDN delivered straight to your inbox.The newsletter is offered in English only at the moment.
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