Function leftJoinHeterogeneous

  • Performs a left outer join on two heterogeneous sequences.

    Type Parameters

    • TFirst
    • TSecond
    • TKey
    • TResult

    Parameters

    • first: Iterable<TFirst>

      The first sequence of the join operation.

    • second: Iterable<TSecond>

      The second sequence of the join operation.

    • firstKeySelector: (item: TFirst) => TKey

      Function that projects the key given an element from first.

    • secondKeySelector: (item: TSecond) => TKey

      Function that projects the key given an element from second.

    • firstSelector: (item: TFirst) => TResult

      Function that projects the result given just an element from first where there is no corresponding element in second.

    • bothSelector: (a: TFirst, b: TSecond) => TResult

      Function that projects the result given an element from first and an element from second that match on a common key.

    • OptionalequalityComparer: EqualityComparer<TKey>

      A function to compare keys.

    Returns IEnumerable<TResult>

    A sequence containing results projected from a left outer join of the two input sequences.

    type Person = { name: string };
    type Pet = { name: string; owner: Person };

    const magnus: Person = { name: 'Magnus' };
    const terry: Person = { name: 'Terry' };
    const adam: Person = { name: 'Adam' };
    const john: Person = { name: 'John' };

    const barley: Pet = { name: 'Barley', owner: terry };
    const boots: Pet = { name: 'Boots', owner: terry };
    const whiskers: Pet = { name: 'Whiskers', owner: adam };
    const daisy: Pet = { name: 'Daisy', owner: magnus };
    const scratchy: Pet = { name: 'Scratchy', owner: { name: 'Bob' } };

    const people = from([magnus, terry, adam, john]);
    const pets = from([barley, boots, whiskers, daisy, scratchy]);

    const result = leftJoinHeterogeneous<Pet, Person, { ownerName: string; pet: string | null }>(
    people,
    pets,
    person => person,
    pet => pet.owner,
    person => ({ ownerName: person.name, pet: null }),
    (person, pet) => ({ ownerName: person.name, pet: pet.name })
    )
    .toArray();

    expect(result).toEqual([
    { ownerName: 'Magnus', pet: 'Daisy' },
    { ownerName: 'Terry', pet: 'Barley' },
    { ownerName: 'Terry', pet: 'Boots' },
    { ownerName: 'Adam', pet: 'Whiskers' },
    { ownerName: 'John', pet: null }
    ]);

    TFirst The type of elements in the first sequence.

    TSecond The type of elements in the second sequence.

    TKey The type of the key returned by the key selector functions.

    TResult The type of the result elements.