returned value from AJAX - Bug or Feature?
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For a long time, I wondered whether one could get data out of the AJAX callback, but the internet said no.
Now, a colleague of mine seems to have found a way to do so, but I wonder whether this is a bug or a feature?
I wrote a little ES7 testcode working inside our tool to confirm it, it looks like this:
async function testWrapper(){
var test = await testPromiseResolve()
console.log("async function was resolved to", test)
}
function testPromiseResolve(){
return $.post('../include/Stornieren/retrieveUserID.php', {
//nothing to transmit
}).then((data) => {
data = JSON.parse(data)
console.log("data from testajax is", data)
return data
})both console logs return the data correctly (here, just a user ID fetched from the database). So the data must have been extracted from inside the promise returned by the jqueryAJAX $.post.
I want to know whether this behavior is a bug or a feature because if its a bug, I can't really use it inside our code since the day may come where this bug is fixed and then the whole thing comes crashing down on me ^^
Also, I couldn't really test whether this code keeps the functionality of async/await. When using return inside promises (I think I should use resolve/reject instead but I must admit that I haven't fully understood how these work inside jqueryAJAX) I might knock out the promise functionality and therefore, when the code really NEEDS to wait for the completion of an AJAX before proceeding, this might pose a risk for the future reliability of the code when database interactions might take longer etc..
ajax async-await ecmascript-7
asked Nov 21 at 8:27
JSONBUG123
487
|
show 2 more comments
up vote
0
down vote
favorite
For a long time, I wondered whether one could get data out of the AJAX callback, but the internet said no.
Now, a colleague of mine seems to have found a way to do so, but I wonder whether this is a bug or a feature?
I wrote a little ES7 testcode working inside our tool to confirm it, it looks like this:
async function testWrapper(){
var test = await testPromiseResolve()
console.log("async function was resolved to", test)
}
function testPromiseResolve(){
return $.post('../include/Stornieren/retrieveUserID.php', {
//nothing to transmit
}).then((data) => {
data = JSON.parse(data)
console.log("data from testajax is", data)
return data
})both console logs return the data correctly (here, just a user ID fetched from the database). So the data must have been extracted from inside the promise returned by the jqueryAJAX $.post.
I want to know whether this behavior is a bug or a feature because if its a bug, I can't really use it inside our code since the day may come where this bug is fixed and then the whole thing comes crashing down on me ^^
Also, I couldn't really test whether this code keeps the functionality of async/await. When using return inside promises (I think I should use resolve/reject instead but I must admit that I haven't fully understood how these work inside jqueryAJAX) I might knock out the promise functionality and therefore, when the code really NEEDS to wait for the completion of an AJAX before proceeding, this might pose a risk for the future reliability of the code when database interactions might take longer etc..
ajax async-await ecmascript-7
asked Nov 21 at 8:27
JSONBUG123
487
What do you mean by "data must have been extracted from inside the promise"? Yes, that's exactly whatawaitis supposed to do; it works just like.then().
– Bergi
Nov 21 at 10:38
I read in numerous answers on stackoverflow that returning a value from a promise shall be impossible. Basically "what happens in callback, stays in callback" (although we dont call this callback anymore^^). Await expects a promise and once its been delivered, code execution moves on. I even had posted questions here where I was told again and again that a value cant be returned from "inside the promise". Sry if its hard to follow what I mean, but I also find it hard to explain it^^
– JSONBUG123
Nov 21 at 11:06
The whole code that runs after anawaitexpression is conceptually in a.then()callback. That's why anasync functioncall must return a promise, it can't return the result immediately either.
– Bergi
Nov 21 at 14:35
ok, but DOES it return the result at all? I mean it does here, somehow, but I wonder whether it actually works like this: "ES7 synchronization functionality + returning the result from the then callback" or if the syntax above just breaks the whole async/await and promise functionality?
– JSONBUG123
Nov 21 at 14:50
No, the call totestWrapper()in your example does not return the result. It just creates a promise, and will log thetestPromiseResolve()result later. I does not stop execution, it does not break anything. What you see there is exactly theasync/awaitfunctionality: it can stop (and defer) the execution inside theasync functionbody only.
– Bergi
Nov 21 at 14:53
|
show 2 more comments
up vote
0
down vote
favorite
up vote
0
down vote
favorite
For a long time, I wondered whether one could get data out of the AJAX callback, but the internet said no.
Now, a colleague of mine seems to have found a way to do so, but I wonder whether this is a bug or a feature?
I wrote a little ES7 testcode working inside our tool to confirm it, it looks like this:
async function testWrapper(){
var test = await testPromiseResolve()
console.log("async function was resolved to", test)
}
function testPromiseResolve(){
return $.post('../include/Stornieren/retrieveUserID.php', {
//nothing to transmit
}).then((data) => {
data = JSON.parse(data)
console.log("data from testajax is", data)
return data
})both console logs return the data correctly (here, just a user ID fetched from the database). So the data must have been extracted from inside the promise returned by the jqueryAJAX $.post.
I want to know whether this behavior is a bug or a feature because if its a bug, I can't really use it inside our code since the day may come where this bug is fixed and then the whole thing comes crashing down on me ^^
Also, I couldn't really test whether this code keeps the functionality of async/await. When using return inside promises (I think I should use resolve/reject instead but I must admit that I haven't fully understood how these work inside jqueryAJAX) I might knock out the promise functionality and therefore, when the code really NEEDS to wait for the completion of an AJAX before proceeding, this might pose a risk for the future reliability of the code when database interactions might take longer etc..
ajax async-await ecmascript-7
asked Nov 21 at 8:27
JSONBUG123
487
For a long time, I wondered whether one could get data out of the AJAX callback, but the internet said no.
Now, a colleague of mine seems to have found a way to do so, but I wonder whether this is a bug or a feature?
I wrote a little ES7 testcode working inside our tool to confirm it, it looks like this:
async function testWrapper(){
var test = await testPromiseResolve()
console.log("async function was resolved to", test)
}
function testPromiseResolve(){
return $.post('../include/Stornieren/retrieveUserID.php', {
//nothing to transmit
}).then((data) => {
data = JSON.parse(data)
console.log("data from testajax is", data)
return data
})both console logs return the data correctly (here, just a user ID fetched from the database). So the data must have been extracted from inside the promise returned by the jqueryAJAX $.post.
I want to know whether this behavior is a bug or a feature because if its a bug, I can't really use it inside our code since the day may come where this bug is fixed and then the whole thing comes crashing down on me ^^
Also, I couldn't really test whether this code keeps the functionality of async/await. When using return inside promises (I think I should use resolve/reject instead but I must admit that I haven't fully understood how these work inside jqueryAJAX) I might knock out the promise functionality and therefore, when the code really NEEDS to wait for the completion of an AJAX before proceeding, this might pose a risk for the future reliability of the code when database interactions might take longer etc..
async function testWrapper(){
var test = await testPromiseResolve()
console.log("async function was resolved to", test)
}
function testPromiseResolve(){
return $.post('../include/Stornieren/retrieveUserID.php', {
//nothing to transmit
}).then((data) => {
data = JSON.parse(data)
console.log("data from testajax is", data)
return data
}) async function testWrapper(){
var test = await testPromiseResolve()
console.log("async function was resolved to", test)
}
function testPromiseResolve(){
return $.post('../include/Stornieren/retrieveUserID.php', {
//nothing to transmit
}).then((data) => {
data = JSON.parse(data)
console.log("data from testajax is", data)
return data
})ajax async-await ecmascript-7
ajax async-await ecmascript-7
asked Nov 21 at 8:27
JSONBUG123
487
asked Nov 21 at 8:27
JSONBUG123
487
asked Nov 21 at 8:27
JSONBUG123
487
asked Nov 21 at 8:27
JSONBUG123
487
asked Nov 21 at 8:27
JSONBUG123
487
487
What do you mean by "data must have been extracted from inside the promise"? Yes, that's exactly whatawaitis supposed to do; it works just like.then().
– Bergi
Nov 21 at 10:38
I read in numerous answers on stackoverflow that returning a value from a promise shall be impossible. Basically "what happens in callback, stays in callback" (although we dont call this callback anymore^^). Await expects a promise and once its been delivered, code execution moves on. I even had posted questions here where I was told again and again that a value cant be returned from "inside the promise". Sry if its hard to follow what I mean, but I also find it hard to explain it^^
– JSONBUG123
Nov 21 at 11:06
The whole code that runs after anawaitexpression is conceptually in a.then()callback. That's why anasync functioncall must return a promise, it can't return the result immediately either.
– Bergi
Nov 21 at 14:35
ok, but DOES it return the result at all? I mean it does here, somehow, but I wonder whether it actually works like this: "ES7 synchronization functionality + returning the result from the then callback" or if the syntax above just breaks the whole async/await and promise functionality?
– JSONBUG123
Nov 21 at 14:50
No, the call totestWrapper()in your example does not return the result. It just creates a promise, and will log thetestPromiseResolve()result later. I does not stop execution, it does not break anything. What you see there is exactly theasync/awaitfunctionality: it can stop (and defer) the execution inside theasync functionbody only.
– Bergi
Nov 21 at 14:53
|
show 2 more comments
What do you mean by "data must have been extracted from inside the promise"? Yes, that's exactly whatawaitis supposed to do; it works just like.then().
– Bergi
Nov 21 at 10:38
I read in numerous answers on stackoverflow that returning a value from a promise shall be impossible. Basically "what happens in callback, stays in callback" (although we dont call this callback anymore^^). Await expects a promise and once its been delivered, code execution moves on. I even had posted questions here where I was told again and again that a value cant be returned from "inside the promise". Sry if its hard to follow what I mean, but I also find it hard to explain it^^
– JSONBUG123
Nov 21 at 11:06
The whole code that runs after anawaitexpression is conceptually in a.then()callback. That's why anasync functioncall must return a promise, it can't return the result immediately either.
– Bergi
Nov 21 at 14:35
ok, but DOES it return the result at all? I mean it does here, somehow, but I wonder whether it actually works like this: "ES7 synchronization functionality + returning the result from the then callback" or if the syntax above just breaks the whole async/await and promise functionality?
– JSONBUG123
Nov 21 at 14:50
No, the call totestWrapper()in your example does not return the result. It just creates a promise, and will log thetestPromiseResolve()result later. I does not stop execution, it does not break anything. What you see there is exactly theasync/awaitfunctionality: it can stop (and defer) the execution inside theasync functionbody only.
– Bergi
Nov 21 at 14:53
What do you mean by "data must have been extracted from inside the promise"? Yes, that's exactly what
await is supposed to do; it works just like .then().– Bergi
Nov 21 at 10:38
What do you mean by "data must have been extracted from inside the promise"? Yes, that's exactly what
await is supposed to do; it works just like .then().– Bergi
Nov 21 at 10:38
I read in numerous answers on stackoverflow that returning a value from a promise shall be impossible. Basically "what happens in callback, stays in callback" (although we dont call this callback anymore^^). Await expects a promise and once its been delivered, code execution moves on. I even had posted questions here where I was told again and again that a value cant be returned from "inside the promise". Sry if its hard to follow what I mean, but I also find it hard to explain it^^
– JSONBUG123
Nov 21 at 11:06
I read in numerous answers on stackoverflow that returning a value from a promise shall be impossible. Basically "what happens in callback, stays in callback" (although we dont call this callback anymore^^). Await expects a promise and once its been delivered, code execution moves on. I even had posted questions here where I was told again and again that a value cant be returned from "inside the promise". Sry if its hard to follow what I mean, but I also find it hard to explain it^^
– JSONBUG123
Nov 21 at 11:06
The whole code that runs after an
await expression is conceptually in a .then() callback. That's why an async function call must return a promise, it can't return the result immediately either.– Bergi
Nov 21 at 14:35
The whole code that runs after an
await expression is conceptually in a .then() callback. That's why an async function call must return a promise, it can't return the result immediately either.– Bergi
Nov 21 at 14:35
ok, but DOES it return the result at all? I mean it does here, somehow, but I wonder whether it actually works like this: "ES7 synchronization functionality + returning the result from the then callback" or if the syntax above just breaks the whole async/await and promise functionality?
– JSONBUG123
Nov 21 at 14:50
ok, but DOES it return the result at all? I mean it does here, somehow, but I wonder whether it actually works like this: "ES7 synchronization functionality + returning the result from the then callback" or if the syntax above just breaks the whole async/await and promise functionality?
– JSONBUG123
Nov 21 at 14:50
No, the call to
testWrapper() in your example does not return the result. It just creates a promise, and will log the testPromiseResolve() result later. I does not stop execution, it does not break anything. What you see there is exactly the async/await functionality: it can stop (and defer) the execution inside the async function body only.– Bergi
Nov 21 at 14:53
No, the call to
testWrapper() in your example does not return the result. It just creates a promise, and will log the testPromiseResolve() result later. I does not stop execution, it does not break anything. What you see there is exactly the async/await functionality: it can stop (and defer) the execution inside the async function body only.– Bergi
Nov 21 at 14:53
|
show 2 more comments
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What do you mean by "data must have been extracted from inside the promise"? Yes, that's exactly what
awaitis supposed to do; it works just like.then().– Bergi
Nov 21 at 10:38
I read in numerous answers on stackoverflow that returning a value from a promise shall be impossible. Basically "what happens in callback, stays in callback" (although we dont call this callback anymore^^). Await expects a promise and once its been delivered, code execution moves on. I even had posted questions here where I was told again and again that a value cant be returned from "inside the promise". Sry if its hard to follow what I mean, but I also find it hard to explain it^^
– JSONBUG123
Nov 21 at 11:06
The whole code that runs after an
awaitexpression is conceptually in a.then()callback. That's why anasync functioncall must return a promise, it can't return the result immediately either.– Bergi
Nov 21 at 14:35
ok, but DOES it return the result at all? I mean it does here, somehow, but I wonder whether it actually works like this: "ES7 synchronization functionality + returning the result from the then callback" or if the syntax above just breaks the whole async/await and promise functionality?
– JSONBUG123
Nov 21 at 14:50
No, the call to
testWrapper()in your example does not return the result. It just creates a promise, and will log thetestPromiseResolve()result later. I does not stop execution, it does not break anything. What you see there is exactly theasync/awaitfunctionality: it can stop (and defer) the execution inside theasync functionbody only.– Bergi
Nov 21 at 14:53