Function predicate

packages/core/src/tests/extras.spec.ts:61–61

    // indexes = 0, 1, 2, 3, 4, 5, 6, 7, 8, 9,10,11,12,13,14
    const arr = [0, 1, 1, 1, 1, 1, 1, 0, 1, 1, 1, 1, 1, 1, 0];
    const predicate = v => v === 0;

    expect(findIndex(arr, predicate)).toBe(0);
    expect(findIndex(arr, predicate, 0)).toBe(0);