What would be the best way to refactor this reduce method using TypeScript?

I'm currently in the process of converting some react native code to typescript, and I've encountered issues with certain reduce functions. How can I refactor this code to avoid type errors during execution?

I have experimented with different approaches to typing both the function and its expected output, but haven't been successful yet.

myArray: data.items.reduce( (map: object, obj: myInterface) : object  => { map[obj.id] = obj; return map; }, [])

The 'myArray' property of my object should be filled with an array of items defined in 'myInterface'. However, when I try to run the code, I encounter the following error:

TypeScript error in MyPath/:

Element implicitly has an 'any' type because expression of type 'number' can't be used to index type '{}'.
  No index signature with a parameter of type 'number' was found on type '{}'.  TS7053

    128 |                 appVersion: data.version || "",
    129 |                 offline: false,
    130 |                 myArray: data.items.reduce( (map: object, obj: myInterface) : object  => { map[obj.id] = obj; return map; }, [])
        |                                                                                           ^
    131 |             });

Answer №1

Thanks to Patrick Robert's answer, the issue has been resolved!

Transforming myArray using data.items.reduce() has greatly improved readability:

Answer №2

Your map must be an object type in order to use it as the initial value for the reduce function.

myArray: data.items.reduce(
   (map: Record<myInterface['id'], myInterface>, obj: myInterface): Record<myInterface['id'], myInterface>  => 
         { map[obj.id] = obj; return map; }, 
    {})

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