Theo's Typesafe Cult•3y ago

nested push-or-create-array in zustand and immer

Is there an easier way to accomplish this with zustand and immer, ie avoiding the conditional? this is inside a zustand create with immer middleware.

// StateType = { knownPaths: { [key: string]: string[] }; };

addPath(region, location) {
    set((state) => {
        if (region in state.knownPaths) {
            state.knownPaths[region].push(location);
        } else {
            state.knownPaths[region] = [location];
        }
    });
},

// StateType = { knownPaths: { [key: string]: string[] }; };

addPath(region, location) {
    set((state) => {
        if (region in state.knownPaths) {
            state.knownPaths[region].push(location);
        } else {
            state.knownPaths[region] = [location];
        }
    });
},

9 Replies

haris•3y ago

Do you need any duplicates in this array? If not I think a Map would work really really well here

scatterOP•3y ago

semantically no, but this has parity with a Json table in my db, which should also never have duplicates but it's not enforced

haris•3y ago

Then yeah, I recommend a Map Would work very well here as you can just do .set iirc, don't have to check if it exists or not to change it

scatterOP•3y ago

i'm not exactly seeing how a map would help, but something like {knownPaths: {[key: string]: Set<string>}} might

haris•3y ago

Wait is knownPaths an Object or an Array?

scatterOP•3y ago

an object whose keys map to arrays Map<string, Set<string>> is probably what i want here actually but then idk if immer can drill down into sets which are map values like that

haris•3y ago

Or wait I'm dumb, Map wouldn't work in the way I thought initially Just woke up sorry This does make sense, but I've never used Immer so no clue if the second thing would work

scatterOP•3y ago

no worries 😄 i'll keep digging, i'm new to immer myself so it feels like i'm just missing something

CaptainStarz•3y ago

https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Operators/Logical_nullish_assignment probably will help

Logical nullish assignment (??=) - JavaScript | MDN

The logical nullish assignment (x ??= y) operator only assigns if x is nullish (null or undefined).

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nested push-or-create-array in zustand and immer