rotate-char.js

// The rotateCharacter function takes a character and a shift value as input.
// If the character is a letter (either uppercase or lowercase),
// it rotates the character by the specified shift value within the alphabet,
// considering wrapping around if necessary. Non-letter characters are returned unchanged.

// This function is commonly used for weak text encryption and decryption,
// where shifting characters by a certain value can obscure their meaning or reveal hidden messages.

// Acceptance criteria:

function rotateCharacter(char, shift) {
  const alphabetLower = [
    "a",
    "b",
    "c",
    "d",
    "e",
    "f",
    "g",
    "h",
    "i",
    "j",
    "k",
    "l",
    "m",
    "n",
    "o",
    "p",
    "q",
    "r",
    "s",
    "t",
    "u",
    "v",
    "w",
    "x",
    "y",
    "z",
  ];
  const alphabetUpper = [
    "A",
    "B",
    "C",
    "D",
    "E",
    "F",
    "G",
    "H",
    "I",
    "J",
    "K",
    "L",
    "M",
    "N",
    "O",
    "P",
    "Q",
    "R",
    "S",
    "T",
    "U",
    "V",
    "W",
    "X",
    "Y",
    "Z",
  ];
  if (alphabetLower.includes(char)) {
    const value = (alphabetLower.indexOf(char) + shift) % 26;
    return alphabetLower[value];
  } else if (alphabetUpper.includes(char)) {
    const value = (alphabetUpper.indexOf(char) + shift) % 26;
    return alphabetUpper[value];
  } else {
    return char;
  }
}

// Given a character (char) and a shift value (shift),
// When the function rotateCharacter is called with these inputs,
// Then it should:

// Scenario: Rotate Lowercase Letters:
// Given a lowercase letter character (char) and a positive integer shift,
// When the function is called with these inputs,
// Then it should rotate the lowercase letter by shift positions within the lowercase alphabet, wrapping around if necessary, and return the rotated lowercase letter as a string.
console.log(rotateCharacter("a", 3)); // Output: "d"
console.log(rotateCharacter("f", 1)); // Output: "g"

// Scenario: Rotate Uppercase Letters:
// Given an uppercase letter character (char) and a positive integer shift,
// When the function is called with these inputs,
// Then it should rotate the uppercase letter by shift positions within the uppercase alphabet, wrapping around if necessary, and return the rotated uppercase letter as a string.
console.log(rotateCharacter("A", 3)); // Output: "D"
console.log(rotateCharacter("F", 1)); // Output: "G"

// Scenario: Leave Non-Letter Characters Unchanged:
// Given a character (char) that is not a letter (neither uppercase nor lowercase) and any positive or negative shift value,
// When the function is called with these inputs,
// Then it should return the character unchanged.
// This specification outlines the behavior of the rotateCharacter function for different input scenarios, including valid and invalid characters, and defines the expected output or action for each case.
console.log(rotateCharacter("7", 5)); // Output: "7" (unchanged, not a letter)

// Scenario: Shifting a Character with Wraparound
// Given a character char within the lowercase alphabet range (e.g., 'z') or the uppercase alphabet range (e.g., 'Z'),
// And a positive integer shift that causes the character to wrap around the alphabet when rotated (e.g., a shift of 3 for 'z' or 'Z'),
// When the rotateCharacter function is called with char and shift as inputs,
// Then it should correctly rotate the character by shift positions within the alphabet while handling the wraparound,
// And the function should return the rotated character as a string (e.g., 'z' rotated by 3 should become 'c', 'Z' rotated by 3 should become 'C').
console.log(rotateCharacter("z", 1)); // Output: "a" (unchanged, not a letter)