JavaScript: Check whether a given string contains only Latin letters and no two uppercase and no two lowercase letters are in adjacent positions

JavaScript Basic: Exercise-101 with Solution

Check Latin Letters with No Adjacent Upper/Lower Case

Write a JavaScript program to check whether a given string contains only Latin letters and no two uppercase and no two lowercase letters are in adjacent positions.

Visual Presentation:

Sample Solution:

JavaScript Code:

// Function to test a string
function test_string(input_str) {

  // Function to check if symbol is lowercase
  var is_lower_case = function(symbol) {
    if ('a' <= symbol && symbol <= 'z') {
      return true;
    }
    return false;
  }

  // Function to check if symbol is uppercase
  var is_upper_case = function(symbol) {
    if ('A' <= symbol && symbol <= 'Z') {
      return true;
    }
    return false;
  }

  // Check if the first character is lowercase or uppercase
  var is_first_char_lower = is_lower_case(input_str[0]),
    is_first_char_upper = is_upper_case(input_str[0]);

  // If the first character is neither lowercase nor uppercase, return false
  if (!(is_first_char_lower || is_first_char_upper)) {
    return false;
  }

  // Iterate through the string
  for (var i = 1; i < input_str.length; i++) {
    // Check odd positions
    if (i % 2) {
      // Check if the character's case differs from the first character's case
      if (is_lower_case(input_str[i]) === is_first_char_lower ||
        is_upper_case(input_str[i]) === is_first_char_upper) {
        return false; // Return false if cases are the same
      }
    } else {
      // Check if the character's case matches the first character's case
      if (is_lower_case(input_str[i]) !== is_first_char_lower ||
        is_upper_case(input_str[i]) !== is_first_char_upper) {
        return false; // Return false if cases do not match
      }
    }
  }

  return true; // Return true if conditions are met for the entire string
}

console.log(test_string('xYr'));   // Example usage
console.log(test_string('XXyx'));  // Example usage   

Output:

true
false

Live Demo:

See the Pen javascript-basic-exercise-101 by w3resource (@w3resource) on CodePen.

Flowchart:

ES6 Version:

// Function to test a string based on specific conditions
const test_string = (input_str) => {

  // Function to check if a symbol is a lowercase letter
  const is_lower_case = (symbol) => {
    if ('a' <= symbol && symbol <= 'z') {
      return true;
    }
    return false;
  }

  // Function to check if a symbol is an uppercase letter
  const is_upper_case = (symbol) => {
    if ('A' <= symbol && symbol <= 'Z') {
      return true;
    }
    return false;
  }

  // Determine if the first character is lowercase or uppercase
  const is_first_char_lower = is_lower_case(input_str[0]);
  const is_first_char_upper = is_upper_case(input_str[0]);

  // If the first character is neither lowercase nor uppercase, return false
  if (!(is_first_char_lower || is_first_char_upper)) {
    return false;
  }

  // Iterate through the string and check conditions based on index and character case
  for (let i = 1; i < input_str.length; i++) {
    if (i % 2) {
      if ((is_lower_case(input_str[i]) === is_first_char_lower) ||
        (is_upper_case(input_str[i]) === is_first_char_upper)) {
        return false;
      }
    } else {
      if ((is_lower_case(input_str[i]) !== is_first_char_lower) ||
        (is_upper_case(input_str[i]) !== is_first_char_upper)) {
        return false;
      }
    }
  }

  // If all conditions are met, return true
  return true;
}

console.log(test_string('xYr'));   // Example usage
console.log(test_string('XXyx'));   // Example usage

For more Practice: Solve these Related Problems:

• Write a JavaScript program that verifies a string contains only Latin letters and that no two adjacent letters share the same case using regular expressions.
• Write a JavaScript function that checks if a string follows an alternating pattern of uppercase and lowercase letters for all Latin characters.
• Write a JavaScript program that scans a string and returns true only if every letter alternates in case and no two consecutive letters are both uppercase or both lowercase.

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