Angular 🇺🇦 - practical notes

Factory async function with ability of cancelling

#js #promise #AbortController

function asyncWithAbort(promiseFn, signal){
  if (signal?.aborted){
    return Promise.reject(new DOMException("Aborted", "AbortError"));
  }
  return new Promise((resolve, reject) => {
    promiseFn().then(resovle).catch(reject);
 
    signal?.addEventListener("abort", () => {
      reject(new DOMException("Aborted", "AbortError"));
    });
  });
}

✅ Link: https://javascript.plainenglish.io/best-practices-for-using-abortcontroller-87892b72d07e

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Angular 🇺🇦 - practical notes

📄 Real Examples of Promise Patterns

#js #promise

— Promise.all() is ideal when you have multiple asynchronous operations that are independent of each other and need to be performed concurrently.

— Promise.race() Use Promise.race() when you need to respond to whichever promise resolves or rejects first. It's useful in scenarios like timeout implementations.

— Promise.allSettled() is useful when you need to wait for all promises to settle, regardless of whether they resolve or reject.

— Promise.any() returns the first promise that resolves and ignores rejections unless all promises reject.

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Angular 🇺🇦 - practical notes

📄 Good Asynchronous Code

#js #promise

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Angular 🇺🇦 - practical notes

📄 Async/Await Techniques

#js #promise #async #await

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Angular 🇺🇦 - practical notes

📄 Throttling Concurrent Requests

#js #promise

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Angular 🇺🇦 - practical notes

🚳 Interview Questions: Promise object

#js #interview #promise

Problem: Implement a simple version of Promise:

The Promise object is an asynchronous programming solution for handling asynchronous events. Promise objects can represent the status of an asynchronous operation, including:

- pending
- fulfilled
- rejected

Analysis:

🌶The MyPromise class is a custom Promise class whose constructor accepts an executor function as a parameter.
🌽The executor function in the constructor will be executed immediately and accepts two parameters, resolve and reject, which are used to modify the state of the Promise.
🍞The resolve method is used to modify the Promise’s status from “pending” to “fulfilled” and pass the value to subsequent handlers.
🥚The reject method is used to modify the Promise’s status from “pending” to “rejected” and pass the reason to the subsequent handler.
🍳The then method is used to register a callback function to be executed when the Promise is completed or rejected. It accepts two parameters: onFulfilled and onRejected, which are called when the Promise is completed or rejected respectively.
🥩The then method returns a new MyPromise instance to support chained calls. If onFulfilled or onRejected returns a value, it will be used as the resolved value for the next MyPromise instance.
🍔The catch method is the shorthand form of then(null, onRejected).
🍕The isFulfilled method is used to check whether the Promise is in the fulfilled state.
🌮The isRejected method is used to check whether the Promise is in the rejected state.

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Angular 🇺🇦 - practical notes

🚳 Interview Questions: Implement promise.all method

#js #interview #promise

Analysis: Use the Promise.all principle to synchronize the Promise state through the counter and result array.

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Angular 🇺🇦 - practical notes

📵 Create a Cancellable Promise

#js #promise

Create a cancellable promise P with a method cancel such that after we call the method P.cancel(), the promise cannot be resolved now. There should be a way to know that the promise was cancelled and not rejected.

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