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Promise and one strange behaviour [closed]

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I encountered a strange behavior when I defined 4 Promises which the last one is described as just rejected and when I tried to run each promise separately, the last one is fired! This will fire rejection especially when I want to run all Promises (_1 _2 _3) in Promise.all().
I wanted to use catch() for promise_2 in Promise.all([promise.catch((err)=>console.log(err))]).then(...) from handling the error happend in promise_2 without cancelling the operation of other Promises
Thx
const asyncFunction=(timer,callback)=>{
setTimeout(() => {
callback(10)
}, timer);
}
const promise_1=new Promise((resolved,reject)=>{
const date=new Date().getSeconds()
date%2===0?asyncFunction(1000,(value)=>resolved(value)):reject(new Error("hello"))
})
const promise_2=new Promise((resolved,reject)=>{
asyncFunction(2000,(value)=>resolved(value))
})
const promise_3=new Promise((resolved,reject)=>{
asyncFunction(3000,(value)=>resolved(value))
})
const promise_4=new Promise((resolved,reject)=>{
reject(new Error("i am bad"))
})
promise_1.then((value)=>console.log(value))
first in Node
C:\Program Files\nodejs\node.exe .\test.js
Process exited with code 1
Uncaught Error Error: I am bad<--------------------------what is it?this is for promise_4 ,while I didn't call it
second in V8
See here
[in V81

Javascript/JQuery/Output Different output between promise and await when calling endpoint using JQUERY.get [closed]

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Closed 3 years ago.
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I'm getting some mock data from a mock endpoint, using JQuery and promises.
Just for the sake of it, I want to try and make it work with async/await.
I think I managed to find some code that works, although, I don't get the same output ( in chrome browser) in the console.
Here are the two pieces of code :
import $ from 'jquery';
let myPromise = $.get("http://5e2f41529c29c900145db22d.mockapi.io/test/users");
myPromise
.then(
(data) => {
console.log('Success promises: ', data);
}
)
.catch(
(error) => {
console.log('Error : ', error.responseText);
}
);
and
// same as above but with async/await
import $ from 'jquery';
let getUsersFromEndPoint = async function (){
try {
let users = await $.get("http://5e2f41529c29c900145db22d.mockapi.io/test/users");
console.log('Success Async: ' + users);
} catch (error) {
console.log('Error : ', error.responseText);
}
};
getUsersFromEndPoint();
And they output :
I'm not sure what the difference is.
Does anyone know why i get a different output ? and what they both "mean" ?
Thank you !

Both the promise-based code and the async/await are correct, and do the same thing, except a small (and therefore hard-to-spot) difference.
The promise-based version's logger code:
console.log('Success promises: ', data);
...logs the result as you expect.
However, in the async function, the console.log contains a + operator, that casts its second operand (the data) into a string, so all objects get transformed into "[object Object]":
console.log('Success Async: ' + users);
Pass data as the second argument of console.log (as you've done with the promise version), and you'll get the expected result.

Should a Javascript function avoid reject a promise via a ternary condition? [closed]

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I saw a piece of code that looks funny to me. It feels like there are multiple things wrong here. Am I seeing a ternary here returning an error rather than a value? Shouldn't this therefore be an if-else?
const aData = await response.json();
return await new Promise((resolve, reject) => {
(aData.title === aName)
? resolve('A data was found')
: reject(new Error('Incorrect data was returned'));
});

Both resolve and reject just return the value undefined, and your callback function doesn't return anything at all. Using a ternary operator to make it a single expression is rather useless.
For clarity, you should better write
if (aData.title === aName) resolve('A data was found');
else reject(new Error('Incorrect data was returned'));
although really you shouldn't be using the new Promise constructor here at all. Just
const aData = await response.json();
if (aData.title !== aName) throw new Error('Incorrect data was returned');
else return 'A data was found';

javascript async/await version versus Promise version of function doesn't work [closed]

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Closed 5 years ago.
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I implemented a function using async and it doesn't work. It always resolves immediately and result is always undefined.
Here is the original async version:
async function validateOne(item, type, state) {
const validation = VALIDATIONS[type]
const result = !(await validation.check(state[item.name].value, state))
return result || validation.message
}
I couldn't figure out why it wasn't working so I rewrote it using a Promise and it works fine.
function validateOne(item, type, state) {
const validation = VALIDATIONS[type]
return new Promise(resolve => {
validation.check(state[item.name].value, state).then(result =>
resolve(result || validation.message)
)
})
}
I'm confused because in my mind these two implementations should be identical (clearly they are not). Hopefully it is something obvious, thanks in advance for any insights!

I think your async function contains an unnecessary logical not ! operator. Try:
async function validateOne(item, type, state) {
const validation = VALIDATIONS[type]
const result = await validation.check(state[item.name].value, state)
return result || validation.message
}
Alternatively, this can be shortened to:
async function validateOne(item, type, state) {
const validation = VALIDATIONS[type]
return (await validation.check(state[item.name].value, state)) || validation.message
}

Nevermind, I had a typo where one version was negating result and the other wasn't!! They are in fact, apart from that typo, identical!

How can I queue and execute multiple promises asynchronously with a single callback? [closed]

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Closed 6 years ago.
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I am using the http request library got. With this package, http connections are asynchronous, fast, and easy to type out. The "got"cha is that got is a promisified package, which brings up several challenges for me. One is that I don't know how to pass around a reference to the got.
What I need to do is use got together with file streams to download the page contents of several url's. Upon completion of all of these streams, I want to continue in the code.
In this example instead of making an array of promises I am getting an array of response objects.
const getFile = (fileUrl) => {
return new Promise((resolve) => {
got.stream(fileUrl).pipe(fs.createWriteStream(path.basename(fileUrl)))
.on('finish', () => {
successMessage('downloaded ' + fileUrl + '!');
resolve();
});
});
};
// create an array of these got promises
let promises = []
for (let file of body.files) {
promises.push(getFile(file));
}
The reason the getFile helper exists is to wrap the got in a promise so that after performing all of the gots, I can use a promise.all call:
// after all got's have executed
promises.all(promises).then(() => {
console.log('all promises resolved');
}
Looking for assistance understanding how to change the first snippet so that promises.all behaves as anticipated.

The Promise aggregation function is called Promise.all() not promises.all().