JavaScript: Swap the case of each character of a string, upper case to lower and vice versa

JavaScript Array: Exercise-9 with Solution

Swap Case in String

Write a JavaScript program that accepts a string as input and swaps the case of each character. For example if you input 'The Quick Brown Fox' the output should be 'tHE qUICK bROWN fOX'.

Visual Presentation:

Sample Solution:

JavaScript Code:

// Declare and initialize the input string
var str = 'c';

// Define constants for uppercase and lowercase letters
var UPPER = 'ABCDEFGHIJKLMNOPQRSTUVWXYZ';
var LOWER = 'abcdefghijklmnopqrstuvwxyz';

// Initialize an array to store the result
var result = [];

// Iterate through each character in the input string
for (var x = 0; x < str.length; x++) {
  // Check if the current character is an uppercase letter
  if (UPPER.indexOf(str[x]) !== -1) {
    // Convert the uppercase letter to lowercase and add it to the result array
    result.push(str[x].toLowerCase());
  }
  // Check if the current character is a lowercase letter
  else if (LOWER.indexOf(str[x]) !== -1) {
    // Convert the lowercase letter to uppercase and add it to the result array
    result.push(str[x].toUpperCase());
  }
  // If the current character is neither uppercase nor lowercase, add it to the result array as is
  else {
    result.push(str[x]);
  }
}

// Output the joined result array as a string
console.log(result.join(''));

Output:

C

Flowchart:

ES6 Version:

// Declare and initialize the input string
const str = 'c';
// Define constants for uppercase and lowercase letters
const UPPER = 'ABCDEFGHIJKLMNOPQRSTUVWXYZ';
const LOWER = 'abcdefghijklmnopqrstuvwxyz';
// Initialize an array to store the result
const result = [];
// Iterate through each character in the input string
for (let x = 0; x < str.length; x++) {
  // Check if the current character is an uppercase letter
  if (UPPER.indexOf(str[x]) !== -1) {
    // Convert the uppercase letter to lowercase and add it to the result array
    result.push(str[x].toLowerCase());
  }
  // Check if the current character is a lowercase letter
  else if (LOWER.indexOf(str[x]) !== -1) {
    // Convert the lowercase letter to uppercase and add it to the result array
    result.push(str[x].toUpperCase());
  }
  // If the current character is neither uppercase nor lowercase, add it to the result array as is
  else {
    result.push(str[x]);
  }
}
// Output the joined result array as a string
console.log(result.join(''));

Live Demo:

See the Pen JavaScript - Swap the case of each character of a string, upper case to lower and vice versa- array-ex- 9 by w3resource (@w3resource) on CodePen.

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