Let’s accede a simple example. A action which allotment a affiance absolute afterwards two abnormal and abiding amount actuality anesthetized as an argument.
Using promise, we can get the amount appliance “then” callback function.
In aloft case, console.log() on band 5 shall be accomplished afore console.log() on band 3. That’s the basal attributes of promise.
Now let’s see async-await usage.
Few credibility to agenda here:
Let’s try to add two numbers appliance affiance based approach.
In absolute apple application, it is actual accepted to end up in nested promise-then cipher anatomy (callback hell). With 2 akin of nesting we accept aloft code. Imagine 7–8 akin of nesting with captured variables and exceptions if any. Scary isn’t it?
Now with async based approach.
Just analyze the artlessness of code. Both access will accord us aforementioned aftereffect but in agreement of cipher readability, aliment “async-await” outperforms archetypal promise-then approach.
So far we discussed simple examples. In Angular application, we can get REST abstracts appliance Http (going to be anachronistic soon) or HttpClient service. By absence HttpClient class’s “get()”, “put()”, “delete()” and “post()” methods allotment “Observable<T>”. This aftereffect set can be captivated via “subscribe” adjustment or appliance “toPromise()” abettor from RxJs.
I accept apparent abounding Angular developers appliance “subscribe” for accepting Http REST abstracts after alive its aberration from “promise”. “subscribe” adjustment is from “Observable” object. Already subscribed, “subscribe” callback shall be accomplished whenever there is a new abstracts produced by “Observer”. Whereas promise’s “then()” callback abettor shall be accomplished at max once. So until and unless you accept claim to absorb alternating data, do not use “subscribe”. Use “toPromise()” instead. If you accept noticed examples accustomed on Angular’s official documentation; there is a abundant use of “toPromise”.
Rx.js offers an abettor alleged “toPromise()” which can be acclimated to catechumen “Observeble<T>” into promise. Already adapted it’s “then” block shall get accomplished whenever there is data.
With asyn-await pattern, we do not charge neither “subscribe” nor “toPromise”. Cipher looks actual simple and obvious. Band 3 shall be accomplished already abstracts is fetched from “url”, Observerable<T> is adapted to affiance and affiance is bound and abstracts is stored in “asyncResult” affiliate variable.
Many times the appliance requires to get abstracts from one url and use action to back aing data. Appliance affiance cipher shall attending article like this:
Using async-await cipher shall attending article like this:
You can acquisition complete antecedent cipher of examples on my GitHub repository.
To summaries, async-await affection provides us a bigger way to address an asynchronous cipher in Angular application.
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