vendure/shared/unique.ts

/**
 * Returns an array with only unique values. Objects are compared by reference,
 * unless the `byKey` argument is supplied, in which case matching properties will
 * be used to check duplicates
 */
export function unique<T>(arr: T[], byKey?: keyof T): T[] {
    return arr.filter((item, index, self) => {
        return index === self.findIndex(i => {
            if (byKey === undefined) {
                return i === item;
            } else {
                return i[byKey] === item[byKey];
            }
        });
    });
}