Object list XOR

xor.ts

// Find the difference between two lists of objects
const xor = <T>(
    listA: T[],
    listB: T[],
    keys: (keyof T)[] // which obj keys to use for uniqueness check
): T[] => {

    // el -> string (for map key)
    const stringify = el => keys.reduce((str, key) => str + el[key], '')

    // List A el -> map
    const map = listA.reduce((map, el) => {
        const elKey = stringify(el)
        map.set(elKey, el)
        return map
    }, new Map() as Map<string, T>)

    // List B el <- map if has match
    // List B el -> map if unique
    listB.forEach(el => {
        const elKey = stringify(el)
        if (map.has(elKey)) map.delete(elKey)
        else map.set(elKey, el)
    })

    // Now map holds XOR of A & B
    return Array.from(map.values())
}

// TEST

interface Filter {
    subject: string
    operator: string
    operand: number
}

const a: Filter[] = [
    { subject: 'key', operator: '=', operand: 4 },
    { subject: 'key', operator: '=', operand: 5 },
    { subject: 'key', operator: '=', operand: 6 },
]

const b: Filter[] = [
    { subject: 'key', operator: '=', operand: 5 },
    { subject: 'key', operator: '=', operand: 6 },
    { subject: 'key', operator: '=', operand: 7 },
]

const x = xor<Filter>(a, b, ['subject', 'operator', 'operand'])

console.log(x)
/*
[ { subject: 'key', operator: '=', operand: 4 },
  { subject: 'key', operator: '=', operand: 7 } ]
*/