Function toString

src/data-structures/deque/__test__/Deque.test.js:165–165

(value)

    deque.addBack({ value: 2, key: 'test2' });

    const toString = (value) => `${value.key}:${value.value}`;

    expect(deque.toString(toString)).toBe('test1:1,test2:2');
  });