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Created a new object, then put an array after it in a loop to patch a property, it works but I dont know why?

I'm working with JavaScript in Node.js and using Express with some mongoose and following a well known RESTful API tutorial on youtube, I've come to patching the API and have been trying to understand why the following code works for sometime now;
updateItem = {};
for (const changes of req.body) {
updateItem[changes.propName] = changes.value;
}
Product.updateOne({ _id: id }, { $set: updateItem })
The rest is just your standard .then().catch() to send the response status, but I'm lost on how creating the object then placing it before an array works to update a value.
It's my current understanding that the object must be instantiated before use, I couldn't just put brackets there and have it work, even if I wasn't using it to set something later. Then I loop through the changes from the request body which must be an array to allow looping, but here's where I get lost.
Does the array of iterated prop names changes.propName get placed inside the updateItem object which is then set to the changed values from the array of properties that are being changed? Do I need to understand $set syntax more? I'm struggling to pick it apart to make it longer or simpler but better to understand.
This is the json array setup I'm passing for testing through postman if it helps;
[
{
"propName": "name", "value": "placeholder user"
}
]
I was unable to find anything to help me understand the interactions going on here, I haven't seen something like this before either but please redirect me if this has already been asked.

How to get and set a ref for a newly cached related object in Apollo client InMemoryCache?

I have a set of related items like so:
book {
id
...
related_entity {
id
...
}
}
which apollo caches as two separate cache objects, where the related_entity field on book is a ref to an EntityNode object. This is fine, the related entity data is also used elsewhere outside of the context of a book so having it separate works, and everything seems well and good and updates as expected...except in the case where the related entity does not exist on the initial fetch (and thus the ref on the book object is null) and I create one later on.
I've tried adding an update function to the useMutation hook that creates the aforementioned related_entity per their documentation: https://www.apollographql.com/docs/react/caching/cache-interaction/#example-adding-an-item-to-a-list like this:
const [mutateEntity, _i] = useMutation(CREATE_OR_UPDATE_ENTITY,{
update(cache, {data}) {
cache.modify({
id: `BookNode:${bookId}`,
fields: {
relatedEntity(_i) {
const newEntityRef = cache.writeFragment({
fragment: gql`
fragment NewEntity on EntityNode {
id
...someOtherAttr
}`,
data: data.entityData
});
return newEntityRef;
}
}
})
}
});
but no matter what I seem to try, newEntityRef is always undefined, even though the new EntityNode is definitely in the cache and can be read just fine using the exact same fragment. I could give up and just force a refetch of the Book object, but the data is already right there.
Am I doing something wrong/is there a better way?
Barring that is there another way to get a ref for a cached object given you have its identifier?

It looks like this is actually an issue with apollo-cache-persist - I removed it and the code above functions as expected per the docs. It also looks like I could instead update to the new version under a different package name apollo3-cache-persist, but I ended up not needing cache persistence anyway.

Firebase getting the reference

The full path for my reference looks like this
data/-KdWI6HAF0_wh9-NTEpe/films/thelobster/rating
and I can set it with
firebase.database().ref('data/-KdWI6HAF0_wh9-NTEpe/films/thelobster/rating')
.set(5);
The problem is that both the keys -KdWI6HAF0_wh9-NTEpe and thelobster are dynamic.
It makes it more difficult than it should be, is there any way to build this with just the -KdWI6HAF0_wh9-NTEpe key and make the film name a wildcard? Oris there a better way I am missing?

You can use Firebase's child() method:
firebase.database().ref('data').child(key).child('films').child(filmKey).child('rating').set(5);
Alternatively you can use ES6 string interpolation:
firebase.database().ref(`data/${key}/films/${filmKey}/rating`).set(5);

Firebase returns 'key' which is the id used to reference your object. Something like this.
var ref = firebase.database().ref("users/ada");
ref.once("value")
.then(function(snapshot) {
var key = snapshot.key; // "ada"
var childKey = snapshot.child("name/last").key; // "last"
});
You can read more about it here.
For 'thelobster', you can console.log() the data that comes from firebase, check the location of the dynamically changing 'thelobster', set it to a variable, and use the variable in your url.
Because I don't know how your incoming data looks like, I can't provide you with that code.

Updating Chrome storage object key value

I'm creating a Google Chrome extension and I'm saving information using the chrome.storage.sync.set function. According to the API you can create an object and save the information between accounts. While I am not having any trouble creating this object, I am having trouble updating a specific key and syncing the value, without making an entirely separate object for each change.
For example my object looks something like this when logged to the console:
{
profile: {
preferences: {
username: 'my username'
}
}
}
I'd like to simply update the value 'username'.
I've tried doing something like this (I have access to the object through the chrome.storage.sync.set function callback):
_ext.profile.preferences.username = 'my new username';
This does update the object, but does not save and store it.
I have also tried this method:
_ext.profile.preferences.username = 'my new username 2'; /* update the key value */
chrome.storage.sync.set(_ext.profile) /* save the entire object to memory */
This method has not worked either.
What do you think is the problem here? Is it the way in which I'm trying to save the object or is there a better method to having a settings based approach?

If you are calling "get" right away, before the "set" has completed, that could be the problem. Your example does not show a callback being passed to handle completion of the "set".

I stumbled across your post while looking to solve the same issue. I ended up using a similar approach as React Redux state management. Instead of trying to manipulate the stored data, I make a copy then replace it.
var data = {};
chrome.storage.sync.get(function(result){
data = result.storedData;
data.profile.preferences.username = 'my new username';
});
chrome.storage.sync.set({'storedData': data});

Javascript get Scope/Context of caller without passing it

I am using meteorjs and there are so called publications and meteor methods. Inside of these you can access a variable this.connection that holds information about all the http headers and connection you have with the specific user, for example the hostname over which they got access to your site.
As I want to make my application multidomain like slack, I now need to hook the database methods to limit the returned dataset to the right hostname.
Problem: This data is only available inside of the poblication or meteor method.
Is there any way to get the this of the calling method without changing the signatures of all my model functions?
Example:
mySpecialMethodWhereThisIsRight = function(param1) {
console.log(this.connection.httpHeaders.host) //Prints out the servername
modelname.mySelfMadeFunction(someData);
}
modelname = {
mySelfMadeFunction: function (data) {
console.log(this.connection.httpHeaders.host) //prints nothing
# some voodo
console.log(this.connection.httpHeaders.host) //Prints out the hostname
}
}
I am now looking for that "voodo" otherwise I would have to rewrite a lot of functions and the places they are called. (not that easy as there is no refactoring tool for coffeescript that actually works reliably)

Not sure I understood, but if you're able to make changes to the calling methods, would this work for you?
mySpecialMethodWhereThisIsRight = function(param1) {
console.log(this.connection.httpHeaders.host) //Prints out the servername
modelname.mySelfMadeFunction.bind(this)(someData);
}