2021/11/21 (增加連結)
How To Return a Response From Asynchronous Calls in JavaScript : Leverage promises in your asynchronous functions
You don’t know JavaScript until you can beat this game
setTimeout()
fetch()
promise
async / await
Learn how Asynchronous and Synchronous methods differ in JavaScript through file reading
Solution — callback
As you may expect, the solution is callback. Place next readFile() as a callback to the previous readFile()
ES6 introduces Promise & async/await to resolve callback hell (picture on the left)
The Evolution of Async JavaScript: From Callbacks, to Promises, to Async/Await
First, just as you can pass a string or a number as an argument to a function, so too can you pass a reference to a function as an argument. When you do this the function you’re passing as an argument is called a callback function and the function you’re passing the callback function to is called a higher order function.
When you create a new Promise, you’re really just creating a plain old JavaScript object. This object can invoke two methods, then, and catch. Here’s the key. When the status of the promise changes to fulfilled, the function that was passed to .then will get invoked. When the status of a promise changes to rejected, the function that was passed to .catch will be invoked. What this means is that once you create a promise, you’ll pass the function you want to run if the async request is successful to .then. You’ll pass the function you want to run if the async request fails to .catch.
Next let’s add another keyword to let the engine know exactly when a function being invoked is asynchronous and is going to return a promise. Let’s use await. As in, “Hey engine. This function is asynchronous and returns a promise. Instead of continuing on like you typically do, go ahead and ‘await’ the eventual value of the promise and return it before continuing”.
What You Need to Know About Asynchronous Programming in JavaScript
async/await is based on Promises
Promises are based on callbacks
callbacks are the foundation of asynchronous programming in JavaScript
Understanding Asynchronous JavaScript — Callback, Promise and Async-Await
What is a Callback?
What is Promise?
What is Async-Await?
Callbacks, Promises and Async/Await
Callbacks
Promises
Error Handling Strategies
Promise methods
resolve()
reject()
all()
race()
Async/Await
Callback, Promises and Async/Await — Asynchronous code in Javascript
Detect slow and fast asynchronous operations with Javascript
I Looked At Over 1000 JavaScript Projects and Found The Following Errors : Asynchronous Common Errors in JavaScript from 1000+ Projects
Forgetting to check the return value of requests
Missing await in try..catch
A mistake in reading a file with an asynchronous code
Forget catch() method to deal with rejected cases
Not waiting for an async forEach
We forget to close resources in case of a rejection
Running some final code after a promise fulfills/rejects
Callback (in function )
Be the Master of the Event Loop in JavaScript (Part 1): Macrotasks, microtasks, execution contexts, event queues, and rAF
Be the Master of the Event Loop in JavaScript (Part 2): Event bubbling, capturing, and delegation
Be the Master of the Event Loop in JavaScript (Part 3): XMLHttpRequest, fetch, and Axios
Implementing setTimeout using requestAnimationFrame
requestAnimationFrame to force immediate execution
Promises: Illustrative JavaScript Doodle
A Coding Writer’s Guide: An Introduction To ES6 Promises
Promises can come in four different states:
Fulfilled
Rejected
Pending
Settled
Creating a Promise
Understanding Promises in JavaScript : Learn about Promises in JavaScript with practical examples
Promises: The Definitive Guide
use observable instead
A Guide to JavaScript Promises: A whistle-stop tour of all things asynchronous in JavaScript: from callback hell to async/await
Callback Functions, Try and Catch
Promises, Then and Catch
Async and Await
Turning Synchronous Functions Asynchronous
Bonus: Asynchronous Redux
Callbacks vs. Promises in JavaScript
A key difference between the two is when using the callback approach, we’d normally just pass a callback into a function that would then get called upon completion in order to get the result of something. In promises, however, you attach callbacks on the returned promise object.
5 JavaScript Promises Util Functions To Spice Up Your Apps
Emulate a Delay
Break Up a Long-Running Task
Add a Timeout Limit To Promise
Complete Promises in Sequence
Complete Only N Promises Simultaneously
JavaScript Fun with Promise.race()
How can this be used practically?
Benchmarking
Simultaneous executions
Set time limits
Best Practices With JavaScript Promises
Converting Non-Promise Async Code to Promises
Asynchronous Chaining
with aync/await
Using Catch to Catch Errors
with aync/await
Use Finally to Run Code That Should Run Regardless of the Outcome of the Promises
Multiple Asynchronous Calls with Promise.all()
3 most common mistakes when using Promises in JavaScript
Wrapping everything in a Promise constructor
Consecutive thens vs parallel thens
Executing a Promise immediately after creation
[Javascript] ES7 Async Await 聖經 ** 是ES2017 (ES8)
JavaScript Async/Await Explained in 10 Minutes
Async — declares an asynchronous function(async function someName(){…}).
Automatically transforms a regular function into a Promise.
When called async functions resolve with whatever is returned in their body.
Async functions enable the use of await.
Await — pauses the execution of async functions.(var result = await someAsyncCall();).
When placed in front of a Promise call, await forces the rest of the code to wait until that Promise finishes and returns a result.
Await works only with Promises, it does not work with callbacks.
Await can only be used inside async functions.
Handling Errors in Async/Await
Another great thing about Async/Await is that it allows us to catch any unexpected errors in a good old try/catch block.
JavaScript async/await: The Good Part, Pitfalls and How to Use
6 Reasons Why JavaScript’s Async/Await Blows Promises Away (Tutorial)
Implementing the async/await syntax for promise request JavaScript
Writing Async Programs in JavaScript
Promises and Async/await
How to Improve Your Asynchronous JavaScript Code With Async and Await
JavaScript Async/Await and Promises: Explained like you’re five years old
How the new ‘Top Level Await’ feature works in JavaScript
Using a fallback if module loading fails
Using whichever resource loads fastest
Resource initialization
Loading modules dynamically
Using await outside async functions in DevTools?
Advanced Asynchronous Programming in JavaScript : with modern-async
You Can Master Async/Await with 7 Diagrams
The basic usage of async/await .
Then we learn about the ancestor of async, the generator function.
Finally, let’s implement async/await by ourselves.
Fulfilling Promises, and their Errors: Promises, Callbacks, Async / Await, and Error Handling
SolidJS
Designing SolidJS: Suspense: React isn’t the only library capable of stopping time.
Future
From Promises to Futures in Javascript
Fluture.js
Generator (in function)
The differences between JavaScript’s asynchronous API timers
Now You See Me: How To Defer, Lazy-Load And Act With IntersectionObserver
Introducing the Intersection Observer API
we’ll look at how to use the Intersection Observer API to watch for visibility changes for a child element.