I am a software development engineer in test for Infosys. My job is officially to write automated tests in Selenium Webdriver. I'm also a web developer as a hobbyest
First time I used Async/Await was a Vue project with a Java Servlet backend. Plopped await in front of the fetch that connected with my back end, and async in front of vue's mounted() method and squealed in delight when my component rendered with my data base information for the first time.
Multiple moments of triumph at once, first use Async/Await, first success with a servlet, and was still new to Vue.JS.
Software dev at Netflix | DC techie | Conference speaker | egghead Instructor | TC39 Educators Committee | Girls Who Code Facilitator | Board game geek | @laurieontech on twitter
Let's say, you need to sequentially resolve three promises. Callback hell looks like this:
function asyncJob(callback) {
asyncA(xyz, (err, buffer) => {
if (err) { throw err; }
asyncB(buffer, (err, result) => {
if (err) { throw err; }
asyncC(result, (err, response) => {
if (err) { throw err; }
if (response.ok()) { return callback(); }
throw new Error('Could not send result');
});
})
});
}
Now the same with Promises:
const asyncJob = () => asyncA(xyz)
.then((buffer) => asyncB(buffer))
.then((result) => asyncC(result))
.then((response) => {
if (response.ok()) { return Promise.resolve(); }
throw new Error('Could not send result');
});
Reads a lot better, doesn't it? Still, it's pretty terse and has a lot of repetition, so async/await is a big improvement when it comes to reading flow:
const asyncJob = async () => {
const buffer = await asyncA(xyz);
const result = await asyncB(buffer);
const response = await asyncC(result);
if (!response.ok()) {
throw new Error('Could not send result');
}
};
Software dev at Netflix | DC techie | Conference speaker | egghead Instructor | TC39 Educators Committee | Girls Who Code Facilitator | Board game geek | @laurieontech on twitter
.then(...) still takes a callback. So while it reads much more congruently, it's basically still good old callback hell, just in a better suit and with better manners. Async/await is a game changer when it comes to readability of asynchronous code.
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Async/await is so great. No more callback hell ever again.
First time I used Async/Await was a Vue project with a Java Servlet backend. Plopped await in front of the fetch that connected with my back end, and async in front of vue's
mounted()
method and squealed in delight when my component rendered with my data base information for the first time.Multiple moments of triumph at once, first use Async/Await, first success with a servlet, and was still new to Vue.JS.
Ah callback hell. Such fun.
Example?
Let's say, you need to sequentially resolve three promises. Callback hell looks like this:
Now the same with Promises:
Reads a lot better, doesn't it? Still, it's pretty terse and has a lot of repetition, so async/await is a big improvement when it comes to reading flow:
We call the second thenable hell.
I'm a fan of Promise.all as a solution, but I acknowledge async/await is a great option too.
.then(...)
still takes a callback. So while it reads much more congruently, it's basically still good old callback hell, just in a better suit and with better manners. Async/await is a game changer when it comes to readability of asynchronous code.