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@a1300

a1300/README.md

Created June 1, 2025 15:15
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a1300 commented Sep 11, 2025 

type OnlyArrays<T> = {
    [K in keyof T]: T[K] extends any[] ? K : never
}[keyof T]

type ArrayItemType<T> = T extends (infer U)[] ? U : never;

function access<
    T extends object,
    K extends OnlyArrays<T>,
    A extends (a: ArrayItemType<T[K]>) => boolean
>
    (first: T, key: K, func: A): {
        added: Array<ArrayItemType<T[K]>>
         
    } {
        const added = (first[key] as Array<ArrayItemType<T[K]>>).filter(func)

        return {
            added,
        }
}

access(obj, "addresses", (a) => true);

improvement

function access<
  T extends Record<K, any[]>,
  K extends keyof T,
  A extends (a: ArrayItemType<T[K]>) => boolean
>(
  first: T,
  key: K,
  func: A
): {
  added: ArrayItemType<T[K]>[]
} {
  const added = first[key].filter(func);
  return { added };
}

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