exemplar.md

Question 1

Javascript function indexOf returns -1 if there is no match in the string, not a falsy value. The following code can resolve the issue.

function validateString(str) {
  if (str.toLowerCase().indexOf('superman') === -1) {
    throw new Error('String does not contain superman');
  }    
}

Question 2

function isInArray(arr, val) {
  return arr.findIndex((item) => item === val) !== -1
}

Question 3

function formatPhoneNumber(str, delimiter = '-') {
  const cleaned = ('' + str).replace(/\D/g, '');
  const match = cleaned.match(/^(1|)?(\d{3})(\d{3})(\d{4})$/);

  if (match) {
    const intlCode = (match[1] ? '+1 ' : '');

    return [match[2], match[3], match[4]].join(delimiter);
  }

  return null;
}

Question 4

describe('fizzBuzz function test cases', () => {
  test("stop is smaller than start, should throw an invalid arguments error", () => {
    expect(() => fizzBuzz(50, 2)).toThrow("Invalid arguments");
  });
  test("start is smaller than 0, should throw an invalid arguments error", () => {
    expect(() => fizzBuzz(-10, 2)).toThrow("Invalid arguments");
  });
  test("stop is smaller than 0, should throw an invalid arguments error", () => {
    expect(() => fizzBuzz(50, -10)).toThrow(new Error('Invalid arguments'));
  });
  test("In case there is no multiplier of 3 or 5 - 1, 2", () => {
    expect(fizzBuzz(1, 2)).toBe("12");
  });
  test("In case there is multiplier of 3 should append Fizz", () => {
    expect(fizzBuzz(8, 9)).toBe("8Fizz");
  });
  test("In case there is multiplier of 5 should append Buzz", () => {
    expect(fizzBuzz(10, 11)).toBe("Buzz11");
  });
  test("In case there are multipliers of 3 and 5 should include Buzz and Fizz", () => {
    expect(fizzBuzz(3, 5)).toBe("Fizz4Buzz");
  });
});

Question 5

First of all, I used hash function to get the unique integer value from string as defined in hashCode. It returns the same value for the same string. Function intToRGB is now to convert the integer into hexadecimal less than 0xFFFFFF with 0s padded to make it 6 length string.

function hashCode(str) {
  let hash = 0;
  
  for (var i = 0; i < str.length; i++) {
    hash = str.charCodeAt(i) + ((hash << 5) - hash);
  }

  return hash;
}

function intToRGB(i) {
  const c = (i & 0x00FFFFFF).toString(16).toUpperCase();

  return "#00000".substring(0, 7 - c.length) + c;
}

function stringToHexColor(str) {
  return intToRGB(hashCode(str))
}

Question 6

When we click button, i is already 10. To resolve the issue, we need to bind scope to each iteration

(function() {
  for (var i = 0, l = 10; i < l; i++) {
    (function(j) {
      document.getElementById('button-' + j).onclick = function () {
        console.log('Line %s', j);
      };
    })(i)
  }
})();

Question 7

function isIterable(obj) {
  return obj != null && typeof obj[Symbol.iterator] === 'function';
}