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
0
votes
3 answers
Why Promise returns also Resolve on Reject
can someone explain, why Promise fires then() function (and also catch() function) when reject is called?
When resolve is called, only then() is trigger - OK
When reject is called, both then() and catch() function are called - Problem
static…
Martin Kravec
- 187
- 2
- 10
0
votes
1 answer
An analog of async.queue for Async/Await functions
I am modernizing some code. It has a piece to load database implemented as:
var customerQueue = async.queue(insertCustomer, DATABASE_PARALLELISM);
customerQueue.drain = function() {
logger.info('all customers loaded');
…
Moshe Shmukler
- 1,270
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- 43
0
votes
1 answer
How to navigate using path.resolve?
I am inside of a folder src and want to create files insides another folder called dist. Below is what I want to do from inside the src folder. Create a json file inside of dist/JSON/{file goes here}
main
- src
index.js
- dist
- JSON
…
Taylor Austin
- 5,407
- 15
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- 103
0
votes
2 answers
ECMAScript: Lexical Grammar vs Syntactic Grammar
I am having some difficulties understanding the specific difference between Lexical Grammar and Syntactic Grammar in the ECMAScript 2017 specification.
Excerpts from ECMAScript 2017
5.1.2 The Lexical and RegExp Grammars
A lexical grammar for…
Magnus
- 6,791
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- 53
- 84
0
votes
1 answer
ECMAScript 2017: EscapeSequence in StringLiteral
The below excerpts refer to ECMAScript 2017.
10.1 Source Text, Syntax
Escape sequences, like \u000A, will not be interpreted as line terminators (i.e. new lines):
In string literals, regular expression literals, template literals and
identifiers,…
Magnus
- 6,791
- 8
- 53
- 84
0
votes
1 answer
ECMAScript 2017: Where Did "13.2 Creating Function Objects" Go (from ES5)?
In ECMA-262, version 5.x (aka. ECMAScript 5 | ES5), there used to be a section 13.2 called Creating Function Objects.
I have been searching through the latest version of the standard, ECMAScript 2017 (aka. ECMAScript 8 | ES8), but cannot find a…
Magnus
- 6,791
- 8
- 53
- 84
0
votes
2 answers
Promise and await Javascript
I've got a strange problem..
FIrst, take a look at my code:
This one is where I use my await..
case "detail": {
const lineMessages = [];
let item = await this.getItem(postback.id);
let lineMessage =…
Terry Djony
- 1,975
- 4
- 23
- 41
0
votes
1 answer
Jest test Fat Arrow in class missing this
I'm writing unit tests for a Component in Jest and I'm currently just testing functionality.
The class function is as followed:
class Comp extends Component {
fetch = null;
update = async () => {
try {
if(this.fetch)
…
CherryNerd
- 1,258
- 1
- 16
- 38
0
votes
0 answers
Best Practice : Error Handling in Promise in async method
I am using typescript and used promises to maintain synchronous behavior in my code .As per my research though we have try catch bloc around promise we are getting un-handled exception when something goes wrong in our promise…
Lalindu
- 329
- 3
- 17
0
votes
2 answers
handle promise error first level inside try catch
function testPromise(id) {
return new Promise(function(resolve, reject) {
setTimeout(function() {
if (typeof id === 'number') {
resolve(id);
} else {
reject('error');
}
…
Daniel.V
- 2,322
- 7
- 28
- 58
0
votes
0 answers
Error trying to incorporate es2017 in webpack
I am trying to add es2017 to my webpack. My program compiles but I get a syntax error message as in the previous picture. I believe I am missing something but I can not find what. I am trying to run the examples given…
Jose Cabrera Zuniga
- 2,348
- 3
- 31
- 56
0
votes
2 answers
Is it possible to share a const to scope outside a block or closure
Take this example function
async function foo () {
const res = await fetchData()
const out = await processData(res)
return out
}
Imagine that I notice fetchData is slow and I want to quickly profile with a generic timer function /…
david_adler
- 9,690
- 6
- 57
- 97
0
votes
3 answers
Async ES2017 Constructor
What is the most up to date method to ensure that some asynchronous code completes in a class constructor before that class is subsequently used?
Specifically, how would an API client class retrieve an access token before allowing more method calls,…
JD Angerhofer
- 148
- 1
- 13
0
votes
2 answers
not getting correct data from promise
Hello guys I'm using await keyword to wait for the async call to return. My url is a get url so if I call it from my browser a json is returned. The problem is when I try to get data from my code it returns me a promise but I can't figure out how to…
Gardezi
- 2,692
- 2
- 32
- 62
0
votes
3 answers
How to await an array length to change to a specified value?
can I await an array length to change to a specified value in JS.
for example:
Suppose there is a magic function named foo here, and I can use foo like this:
async funtion bar () {
let arr = [];
// Wait for the arr.length to change to 10,…
user9186776
- 1
- 1
- 2