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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

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.

Pictorial Presentation:

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

Sample Solution:

HTML Code:

<!DOCTYPE html>
<html>
<head>
  <meta charset="utf-8">
  <meta name="viewport" content="width=device-width">
  <title> Check whether a given string contains only Latin letters and no two uppercase and no two lowercase letters are in adjacent positions</title>
</head>
<body>

</body>
</html>

JavaScript Code:

function test_string(input_str) {

  var is_lower_case = function(symbol) {
    if ('a' <= symbol && symbol <= 'z') {
      return true;
    }
    return false;
  }

  var is_upper_case = function(symbol) {
    if ('A' <= symbol && symbol <= 'Z') {
      return true;
    }
    return false;
  }

  var is_first_char_lower = is_lower_case(input_str[0]),
    is_first_char_upper = is_upper_case(input_str[0]);

  if (!(is_first_char_lower || is_first_char_upper)) {
    return false;
  }

  for (var 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;
      }
    }
  }

  return true;
}

console.log(test_string('xYr'));   
console.log(test_string('XXyx'));

Sample Output:

true
false

Flowchart:

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

ES6 Version:

function test_string(input_str) {
  const is_lower_case = symbol => {
    if ('a' <= symbol && symbol <= 'z') {
      return true;
    }
    return false;
  };

  const is_upper_case = symbol => {
    if ('A' <= symbol && symbol <= 'Z') {
      return true;
    }
    return false;
  };

  const is_first_char_lower = is_lower_case(input_str[0]);
  const is_first_char_upper = is_upper_case(input_str[0]);

  if (!(is_first_char_lower || is_first_char_upper)) {
    return false;
  }

  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;
      }
    }
  }

  return true;
}

console.log(test_string('xYr'));   
console.log(test_string('XXyx'));

Live Demo:

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


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Previous: Write a JavaScript program to check if there is at least one element which occurs in two given sorted arrays of integers.
Next: Write a JavaScript program to find the number of inversions of a given array of integers.

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JavaScript: Tips of the Day

How to insert an item into an array at a specific index (JavaScript)?

What you want is the splice function on the native array object.

arr.splice(index, 0, item); will insert item into arr at the specified index (deleting 0 items first, that is, it's just an insert). In this example we will create an array and add an element to it into index 2:

var arr = [];
arr[0] = "Jani";
arr[1] = "Hege";
arr[2] = "Stale";
arr[3] = "Kai Jim";
arr[4] = "Borge";

console.log(arr.join());
arr.splice(2, 0, "Lene");
console.log(arr.join());

Ref: https://bit.ly/2BXbp04