Async/Await & UnhandlePromiseRejectWarning [duplicate] - node.js

Question

This question already has answers here:
Using async/await with a forEach loop
(33 answers)
Closed 3 years ago.
I have the following code writed in nodejs express and firebase
route.js
try{
const test = await invoiceData.setAssignsInvoiced();
res.json({
status: true,
message: "Successful Invoice Generation"
});
}catch (e) {
res.status(500).json({
status: false,
message: "Internal Server Error",
data: e
});
}
InvoicesStorage.js
setAssignsInvoiced = async() => {
return new Promise(async (resolve,reject)=>{
try {
await _getAssignsForInvoiced(this);
this.assignsForInvoiced.forEach(async assing => {
let aux = assing._key.path.segments.length;
let ref = assing._key.path.segments[aux - 1];
await _updateAssignsToInvoiced(assing.data(),ref);
});
resolve(true)
} catch (error) {
console.error(error)
reject(error)
}
})
};
const _updateAssignsToInvoiced = async (assing, ref) => {
try {
const { invoiceNum } = assing.data(); //Here's an intentional error
await db
.collection("leadAsign")
.doc(ref)
.update({
invoiced: true,
updateDate: Date.now() - 240 * 60 * 1000,
invoiceNum
});
} catch (error) {
console.error(error);
throw new Error("Error at update to invoiced assigns");
}
};
How I hope it works:
According to me, I should throw out a synchronous error because my code has "await" and stop the system.
The answer I have:
the code runs asynchronously, that is, after calling the function the "await" has no effect and answers a "res.json" with status 200 and it is only after it throws the next error.
TypeError: assing.data is not a function
at _updateAssignsToInvoiced (D:\$Workzone\gd_fridays_h\src\controllers\invoices\InvoicesStorage.js:90:35)
at D:\$Workzone\gd_fridays_h\src\controllers\invoices\InvoicesStorage.js:55:23
at Array.forEach (<anonymous>)
at D:\$Workzone\gd_fridays_h\src\controllers\invoices\InvoicesStorage.js:51:37
true
POST /generateSingle 200 5182.650 ms - 57
(node:5600) UnhandledPromiseRejectionWarning: Error: Error at update to invoiced assigns
at _updateAssignsToInvoiced (D:\$Workzone\gd_fridays_h\src\controllers\invoices\InvoicesStorage.js:102:11)
at D:\$Workzone\gd_fridays_h\src\controllers\invoices\InvoicesStorage.js:55:23
at Array.forEach (<anonymous>)
at D:\$Workzone\gd_fridays_h\src\controllers\invoices\InvoicesStorage.js:51:37
(node:5600) UnhandledPromiseRejectionWarning: Unhandled promise rejection. This error originated either by throwing inside of an async function without a catch block, or by rejecting a promise which was not handled with .catch(). (rejection id: 4)
(node:5600) [DEP0018] DeprecationWarning: Unhandled promise rejections are deprecated. In the future, promise rejections that are not handled will terminate the Node.js process with a non-zero exit code.

Answer 1

async/await doesn't work as you're expecting it to inside a forEach loop. An abundance of info on that specific issue here: https://stackoverflow.com/a/37576787/4043746
To fix your problem, you could use a for/of loop:
setAssignsInvoiced = async () => {
return new Promise(async (resolve, reject) => {
try {
await _getAssignsForInvoiced(this)
for (const assign of this.assignsForInvoiced) {
let aux = assign._key.path.segments.length
let ref = assign._key.path.segments[aux - 1]
await _updateAssignsToInvoiced(assign.data(), ref)
}
resolve(true)
} catch (error) {
console.error(error)
reject(error)
}
})
}
However, I'd also be tempted to suggest not returning a promise, as you're essentially doing that due to it being an async function. Something like this should work and is cleaner imo:
setAssignsInvoiced = async () => {
try {
await _getAssignsForInvoiced(this)
for (const assign of this.assignsForInvoiced) {
let aux = assign._key.path.segments.length
let ref = assign._key.path.segments[aux - 1]
await _updateAssignsToInvoiced(assign.data(), ref)
}
} catch (error) {
console.error(error)
// Re-throwing the error to pass the error down, just like you've
// done inside your _updateAssignsToInvoiced function's catch
throw new Error('Error setting assigns')
}
}

Answer 2

Async/await inside a forEach() loop will not wait until all the async operations inside the loop is completed.
One approach would be using Promise.all() like so:
const setAssignsInvoiced = async () => {
try {
await _getAssignsForInvoiced(this);
await _updateAssignsList(this.assignsForInvoiced);
return true;
} catch (error) {
console.error(error);
return new Error(error);
}
};
const _updateAssignsList = assignsList => {
return Promise.all(
assignsList.map(async assign => {
let aux = assign._key.path.segments.length;
let ref = assign._key.path.segments[aux - 1];
return await _updateAssignsToInvoiced(assign.data(), ref);
})
);
};
I've just extracted the async loop process to a separate function which return a Promise.