iterator.js

const test = require('tape');

class Iterator {
    hasNext() {
        // Your code here
    }
    next()  {
        // Your code here
    }
}

const exampleOne = new Iterator([[1, 2, 3], [], [4, 5, 6]]);
const exampleTwo = new Iterator([[], []]);
const exampleThree = new Iterator([[], [1]]);

test('hasNext()', (t) => {
    t.plan(3);
    t.equal(exampleOne.hasNext(), true);
    t.equal(exampleTwo.hasNext(), false);
    t.equal(exampleThree.hasNext(), true);
});

test('next()', (t) => {
    t.plan(9);
    
    t.equal(exampleOne.next(), 1);
    t.equal(exampleOne.next(), 2);
    t.equal(exampleOne.next(), 3);
    t.equal(exampleOne.next(), 4);
    t.equal(exampleOne.next(), 5);
    t.equal(exampleOne.next(), 6);
    t.equal(exampleOne.next(), null);
    
    t.equal(exampleTwo.next(), null);
    
    t.equal(exampleThree.hasNext(), true);
    t.equal(exmapleThree.next(), 1);
    t.equal(exampleThree.hasNext(), false);
    t.equal(exmapleThree.next(), null);
});