readme.md

Challenge: Reverse String

Instructions

Write a function called reverseString that takes in a string and returns the reverse of that string. In this section, we are really focusing on loops without using any built-in methods, so try that first. If you get stuck, you can always use the built-in methods to solve the problem.

Function Signature

/**
 * Returns the reverse of a string.
 * @param {string} str - The string to reverse.
 * @returns {string} - The reverse of the string.
 */
function reverseString(str: string): string;

Examples

reverseString('hello') // 'olleh'
reverseString('world') // 'dlrow'
reverseString('') // ''

Constraints

• The input string will only contain lowercase letters and spaces

Hints

• You can also do this without using any of the built-in methods and just use a for loop.
• You could also use the methods split, reverse, and join to solve this problem.

Solutions

Click For Solution 1

This solution uses a for loop to reverse the string.

function reverseString(str) {
  let reversed = '';

  for (let i = str.length - 1; i >= 0; i--) {
    reversed += str[i];
  }

  return reversed;
}

Explanation

• Create a variable called reversed and set it equal to an empty string.
• Create a for loop that starts at the last index of str and decrements by 1 until it reaches 0.
• Add the character at the current index to the reversed variable.
• Return the reversed variable.

Click For Solution 2

This solution uses built-in methods to reverse the string.

function reverseString(str) {
  return str.split('').reverse().join('');
}

Explanation

We created a function called reverseString that takes in a string called str. We then return the result of chaining the split, reverse, and join methods on str.

The split function takes in a string and turns it into an array. We passed in an empty string as an argument to split so that it will split the string into an array of characters.(["h", "e", "l", "l", "o"])

The reverse function takes in an array and reverses it. (["o", "l", "l", "e", "h"])

The join function takes in an array and turns it into a string. We passed in an empty string as an argument to join so that it will join the array of characters into a string. ('olleh')

Test Cases

test('Reversing a string', () => {
  expect(reverseString('Hello')).toBe('olleH');
  expect(reverseString('JavaScript')).toBe('tpircSavaJ');
  expect(reverseString('12345')).toBe('54321');
});