How to add elements to a svelte writable store vector - svelte-store

Question

I have this store:
export const flights = writable<APIResponse>([])
And I want to add elements at the end of that array. I tried his:
flights.set({ ...flights, input })
But that doesn't add, it overwrites the existing elements, leaving only the one in input. How can I do that?
I am in a .ts. I'm taking over someone else's job who left the company and I'm new to all of this, I still don't have a clear idea of this mix of languages/frameworks.
When I print flights appears empty.
console.warn(flights store: + JSON.stringify(flights))
{}
Some advances. It seems it was not empty. I wasn't printing it the correct way. I can see the elements added if I add them like this:
unconfirmed_flights.update((data) => {
data.push(input))
return data
})
and print the content like this:
unconfirmed_flights .update((data) => {
console.warn(JSON.stringify(data))
return data
})
That prints something like: [{json_object}, {json_object}].
The thing is that in fact I have two stores:
export const flights = writable<APIResponse>([])
export const unconfirmed_flights = writable<APIResponse>([])
The code receives several items that are added to unconfirmed_flights correctly. Then a dialog opens and if the user presses accept I need to copy the items in unconfirmed_flights to flights. I do that like this. First I create an index (id) with the empty array:
flights.update((data) => {
data[id] = []
return data
})
Then I add all the elements in unconfirmed_flights:
unconfirmed_flights.update((uplan) => {
flights.update((data) => {
data[id].push(uplan)
return data
})
return uplan
})
But the result, instead of
{"id": [{json_object}, {json_object}]}
is
{"id": [[{json_object}, {json_object}]]}
With that nested array. However, if I don't do the step of data[id] = [], I get a "Uncaught (in promise) TypeError: data.push is not a function", that I read is because the index does not exist. How can I avoid that nested array?

Answer 1

const flights = writable([])
If you want to add a value to a store from a .js file use .update() where the current value is available
flights.update(value => [...value, newValue])
Inside a .svelte file the store variable can be prefixed with $ to access the value and the new value could be added like this
$flights = [...$flights, newValue]

Answer 2

After three days of unsuccessful attemps to add the content exactly as I needed, I found the help of a JS expert. There it goes the solution.
Having
flights = {"1": { "name": "name1" } }
and
unconfirmed_flights = [ {"2": { "name": "name2" } }, {"3": { "name": "name3" } } ]
The goal was to add the unconfirmed_flights to flights:
flights = {"1": { "name": "name1" },
"2": { "name": "name2" },
"3": { "name": "name3" } }
And that was done like this:
flights.update((plan) => {
const uplan = get(unconfirmed_flights)
uplan.forEach((uplanItem) => {
plan = { ...plan, ...uplanItem }
})
return plan
})
being
export type APIResponse = { [key: string]: any }
export const flights = writable<APIResponse>([])
export const unconfirmed_flights = writable<APIResponse[]>([])