Usage

diff([1, 2, 3, 4], [2, 4]); // [1, 3]
diff([{ a: 1 }, { a: 2 }, { a: 3 }], [{ a: 2 }, { a: 4 }], (n) => n.a); // [{a:1}, {a:3}]

Installation

CLI

npx atmx add helper diff

Manually

Copy and paste the following method into @/utils/helpers/undefined.ts:

/**
* Returns all items from the first list that do not exist in the
* second list.
*
* @example
* diff([1, 2, 3, 4], [2, 4]) // [1, 3]
* diff([{a:1}, {a:2}, {a:3}], [{a:2}, {a:4}], (n) => n.a) // [{a:1}, {a:3}]
*/
export function diff<T>(
root: readonly T[],
other: readonly T[],
identity: (item: T) => string | number | symbol = (t: T) =>
t as unknown as string | number | symbol,
): T[] {
if (!root?.length && !other?.length) {
return [];
}
if (root?.length === undefined) {
return [...other];
}
if (!other?.length) {
return [...root];
}
const bKeys = other.reduce(
(acc, item) => {
  acc[identity(item)] = true;
  return acc;
},
{} as Record<string | number | symbol, boolean>,
);
return root.filter((a) => !bKeys[identity(a)]);
}