Running a forEach() on an Array of Objects After Retrieving with findOne() in Mongo Back-end - arrays

Question

I am using findOne() to retrieve a document like this:
let staffToUpdate = await Staff.findOne({
_id: request.parameters.id
}).exec();
let historyArray = await crewToUpdate.history;
console.log("historyArray: ", await historyArray);
console.log(Array.isArray(historyArray)); // returns true
The data looks like this:
history: [
{
status: "active",
startDate: <Date>,
endDate: <Date>,
completed: false
},
{
status: "training",
startDate: <Date>,
endDate: <Date>,
completed: true
}
]
When I do the above I get an array of objects printed out, as well as a return of "true" on the check to see if "historyArray" is indeed an array.
So now that I have this array, I'd like to run a transformation on the objects found within it, like so:
let updatedHistoryArray = historyArray.then(
updatedHistoryArray.forEach(history => {
history.completed = true;
history.endDate = new Date();
})
);
However, this is the part that's not working. When I try this I get this error:
Reason: ReferenceError: historyArray is not defined
What am I missing here?
UPDATE: After a suggestion from a commenter below, I tried this:
let staffToUpdate = await Staff.findOne({
_id: request.parameters.id
}).exec();
let staffObject = staffToUpdate.toObject();
let historyArray = await staffObject.history;
console.log(await historyArray); // prints the array
console.log(Array.isArray(historyArray)); // returns true
historyArray.forEach(history => { // this is where the error occurs
history.completed = true;
history.endDate = new Date();
});
With this last block of code I get this error:
Reason: ReferenceError: historyArray is not defined

Answer 1

historyArray is not a Promise and you can not run then on it.
When this code runs
let staffToUpdate = await Staff.findOne({
_id: request.parameters.id
}).exec();
it waits until query is executed and assigns the actual result (mongoose Document), not a promise and assigns it to staffToUpdate. You need to run toObject() on mongoose Document to get plain object without the wrapper:
const unwrappedStaffToUpdate = staffToUpdate.toObject();
After that you don't need to use await on crewToUpdate.history because it is not a Promise and it is synchronious. That is why you can not run then on historyArray because it is a normal Array and not a Promise.
Try this code:
unwrappedStaffToUpdate.historyArray.forEach(history => {
history.completed = true;
history.endDate = new Date();
});
Or if you do not want to mutate your Array use map instead of forEach:
const updatedHistoryArray = unwrappedStaffToUpdate.historyArray.map(history => ({
...history
completed: true;
endDate: new Date()
})
);