92 lines
3.9 KiB
Markdown
92 lines
3.9 KiB
Markdown
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---
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title: Await Promises
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localeTitle: في انتظار الوعود
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---
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## في انتظار الوعود
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يجعل [مشغلي](https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Operators) `async` / `await` من السهل تنفيذ العديد من وعود async. كما أنها تسمح للمهندسين بكتابة أكواد أكثر وضوحًا وإيجازًا وقابلة للاختبار.
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لفهم هذا الموضوع ، يجب أن يكون لديك فهم قوي لكيفية عمل [الوعود](https://guide.freecodecamp.org/javascript/promises) .
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* * *
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## بناء الجملة الأساسي
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\`\` \`جافا سكريبت function slowResolvedPromiseFunc (string) { return new Promise (resol = = { setTimeout (() => { حل (سلسلة)؛ } ، 5000) ؛ })؛ }
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وظيفة async doIt () { const myPromise = await slowResolvedPromiseFunc ("foo")؛ console.log (myPromise)؛ // "foo" }
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افعلها()؛
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``There are a few things to note:
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* The function that encompasses the `await` declaration must include the `async` operator. This will tell the JS interpreter that it must wait until the Promise is resolved or rejected.
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* The `await` operator must be inline, during the const declaration.
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* This works for `reject` as well as `resolve`.
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---
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## Nested Promises vs. `Async` / `Await`
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Implementing a single Promise is pretty straightforward. In contrast, Chained Promises or the creation of a dependency pattern may produce "spaghetti code".
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The following examples assume that the <a href='https://github.com/request/request-promise' target='_blank' rel='nofollow'>`request-promise`</a> library is available as `rp`.
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### Chained/Nested Promises
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``
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جافا سكريبت // الوعد الأول const fooPromise = rp ("http://domain.com/foo")؛
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fooPromise.then (resultFoo => { // يجب انتظار "foo" لحلها console.log (resultFoo)؛
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`const barPromise = rp("http://domain.com/bar");
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const bazPromise = rp("http://domain.com/baz");
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return Promise.all([barPromise, bazPromise]);
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`
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}). then (resultArr => { // تعامل مع "bar" و "baz" هنا console.log (resultArr \[0\])؛ console.log (resultArr \[1\])؛ })؛
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``### `async` and `await` Promises
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``
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جافا سكريبت // لف كل شيء في وظيفة متزامن وظيفة async doItAll () { // انتزاع البيانات من نقطة النهاية "فو" ، ولكن انتظر الحل console.log (في انتظار rp ("http://domain.com/foo"))؛
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`// Concurrently kick off the next two async calls,
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// don't wait for "bar" to kick off "baz"
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const barPromise = rp("http://domain.com/bar");
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const bazPromise = rp("http://domain.com/baz");
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// After both are concurrently kicked off, wait for both
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const barResponse = await barPromise;
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const bazResponse = await bazPromise;
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console.log(barResponse);
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console.log(bazResponse);
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`
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}
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// وأخيرا ، استدعاء الدالة المتزامن doItAll (). ثم (() => console.log ('Done!'))؛
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``The advantages of using `async` and `await` should be clear. This code is more readable, modular, and testable.
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It's fair to note that even though there is an added sense of concurrency, the underlying computational process is the same as the previous example.
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---
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## Handling Errors / Rejection
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A basic try-catch block handles a rejected Promise.
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``
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جافا سكريبت خطأ غير متزامن functionExample () { محاولة { const rejectedPromise = await Promise.reject ("Oh-oh!")؛ } catch (خطأ) { console.log (خطأ)؛ // "اه-اوه!" } }
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errorExample ()؛ \`\` \`
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* * *
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#### معلومات اكثر:
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* `await` مشغل [MDN مستندات](https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Operators/await)
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* `async` Function Operator [MDN Docs](https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Operators/async_function)
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