Use this tag for questions about features finalized in ECMAScript 2017. Do *not* use this tag if the code in question merely *uses* one of the features, *unless* the feature is cause of the problem.
Proposals finalized in 2017 include:
Questions tagged [ecmascript-2017]
387 questions
2
votes
3 answers
async and await and promise in regards to catching errors
I have a question about catching user error in async and wait.
Let say I have a route that only fetches for a single user.
routes.js
routes.get('/getuserbyid/:id', (req, res) => {
const id = req.params.id;
accountController.getById(id)
…
Pak Chu
- 253
- 1
- 5
- 13
2
votes
1 answer
Async Await es6 optimization
I am trying to use async/await and my code works, I just need advice about is it the right way to use async/await, or do I need .then
here. I have a function loadDataForExport - that return promise with generate data. Also, I have actionButtons…
Palaniichuk Dmytro
- 2,943
- 12
- 36
- 66
2
votes
1 answer
Why does ESLint throw parsing error while defining async function as method to existing object and how to prevent it?
Let's assume we have plain object
const foo = {}
and by using Promise constructor syntax we would add async method to it this way:
foo.myAsyncMethod = function () {
return new Promise((resolve, reject) => {
...
})
}
but we can't do this…
Kunok
- 8,089
- 8
- 48
- 89
2
votes
0 answers
Why is an async event handler for a jQuery event not getting called?
I'd like to make use of async/await with fetch in response to my user selecting something from an HTML
ArtOfCode
- 5,702
- 5
- 37
- 56
2
votes
2 answers
Async event and exception
in ES7 we will be having async and await keyword for JS. It looks very promising for regular functions. But how do we handle exception in async events?
for example
async badFunc()
{
throw "bad";
}
var reader = new FileReader();
reader.onload =…
Steve
- 11,696
- 7
- 43
- 81
2
votes
3 answers
What's the right way for handling Async functions for loading a .gif image?
For example, look at this code:
function myPromise() {
return new Promise(resolve => {
setTimeout(() => {
resolve('Stack Overflow');
}, 2000);
});
}
async function sayHello() {
const…
Mohammad
- 4,441
- 3
- 13
- 15
2
votes
2 answers
Using async await on ReactJS with Babel leads to Error: Unexpected token
Wanted to use ES8 async/await for my project. Have been using it recently on ReactNative with Expo so didn't expect any problems on ReactJS. Although, the app can't build now...
This is the error I get:
Syntax error:…
Kirill Stiopin
- 61
- 8
2
votes
1 answer
How to abort running async/await xmlHttpRequest within componentWillUnmount?
This is the code... how would you abort such ajax call?
Or, how to prevent react from giving me an error "setState called on unmounted component"?
(httpGet is just a wrapper for XMLHttpRequest and a promise)
async componentDidMount() {
const…
Ivan Hanák
- 2,214
- 1
- 16
- 25
2
votes
2 answers
Why does Typescript think async/await returns a value wrapped in a promise?
I want to refactor a promise chain into async/await, but Typescript is complaining about the typing.
TS2322:Type 'IHttpPromiseCallbackArg< IResp >' is not assignable to type 'IResp'...
I thought await would return a regular value, not a promise.…
user2954463
- 2,362
- 2
- 23
- 37
2
votes
0 answers
Trying to understand JS async/await
I'm learning async/await and created a small fiddle @ https://jsfiddle.net/mpycio/rb8taLt7/.
const parse = async (num) => {
let res = await new Promise(resolve =>
setTimeout(() => {resolve(num * 2)}, 0)
)
return…
Mahakala
- 761
- 1
- 10
- 16
2
votes
2 answers
async function example() or async example()?
Why writing this is wrong:
'use strict'
async example1 () {
return 'example 1'
}
async example2 () {
return 'example 2'
}
export { example1, example2 }
But it is fine like this:
export default {
async example1 () {
return 'example 1'
…
Run
- 54,938
- 169
- 450
- 748
2
votes
1 answer
assigning to array at different times yields different results
I have these two different codes that are very slightly different but yield different results:
(async () => {
const results = new Array(concurrentBrowsers).fill({});
const browsers = [];
for (let index = 0; index < concurrentBrowsers; index++)…
Michael
- 22,196
- 33
- 132
- 187
2
votes
1 answer
Error with no 'message' after promisfying https.get
I am using ES2017's await keyword, and util.promisify() to use https.get() with await.
Testing connecting to HTTPS with the following code:
const util = require('util'),
https = require('https'),
httpsGet = util.promisify(https.get);
var…
mikemaccana
- 110,530
- 99
- 389
- 494
2
votes
2 answers
Should async/await code be entirely contained with try block?
I've been reading up on the new async/await and have been playing around with it in Node 8. I've come across some people putting everything within the initial try block, and others having only the await and all the rest is below the try/catch. Is…
VirtualWolf
- 653
- 13
- 23
2
votes
1 answer
Reuse object literals created via destructuring
I am trying to reuse the object literals for both async calls. At the end my expect should check the success of the deleteBucket call. Problem is I can't do this, or it says I've got dup variables defined:
it('can delete a bucket', async () => {
…
PositiveGuy
- 17,621
- 26
- 79
- 138