JavaScript: Swap pairs of adjacent digits of a given integer of even length

JavaScript Basic: Exercise-150 with Solution

Write a JavaScript program to swap pairs of adjacent digits of a given integer of even length.

Visual Presentation:

Sample Solution:

JavaScript Code:

/**
 * Function to swap adjacent digits of a number
 * @param {number} n - The input number
 * @returns {(number|boolean)} - The number with adjacent digits swapped or `false` if the length is odd
 */
function swap_adjacent_digits(n) {
    // Check if the length of the number is odd, return `false` in such cases
    if (n.toString().length % 2 != 0) {
        return false;
    }
    var result = 0,
        x = 1;
    // Loop until the number becomes zero
    while (n != 0) {
        // Get the last digit (dg1) and the second last digit (dg2)
        var dg1 = n % 10,
            dg2 = ((n - dg1) / 10) % 10;
        // Swap dg1 and dg2, add to the result with appropriate position
        result += x * (10 * dg1 + dg2);
        // Remove the last two digits from the number
        n = Math.floor(n / 100);
        // Increment the multiplier x by 100
        x *= 100;
    }
    return result; // Return the number with swapped adjacent digits
}

// Test cases
console.log(swap_adjacent_digits(15));  
console.log(swap_adjacent_digits(1234));  
console.log(swap_adjacent_digits(123456));  
console.log(swap_adjacent_digits(12345));  

Output:

51
2143
214365
false

Live Demo:

See the Pen javascript-basic-exercise-150 by w3resource (@w3resource) on CodePen.

Flowchart:

ES6 Version:

/**
 * Function to swap adjacent digits of a number
 * @param {number} n - The input number
 * @returns {(number|boolean)} - The number with adjacent digits swapped or `false` if the length is odd
 */
const swap_adjacent_digits = n => {
    // Check if the length of the number is odd, return `false` in such cases
    if (n.toString().length % 2 !== 0) {
        return false;
    }
    let result = 0,
        x = 1;
    // Loop until the number becomes zero
    while (n !== 0) {
        // Get the last digit (dg1) and the second last digit (dg2)
        const dg1 = n % 10,
            dg2 = ((n - dg1) / 10) % 10;
        // Swap dg1 and dg2, add to the result with appropriate position
        result += x * (10 * dg1 + dg2);
        // Remove the last two digits from the number
        n = Math.floor(n / 100);
        // Increment the multiplier x by 100
        x *= 100;
    }
    return result; // Return the number with swapped adjacent digits
}

// Test cases
console.log(swap_adjacent_digits(15)); // Output: false (length is odd)
console.log(swap_adjacent_digits(1234)); // Output: 2143
console.log(swap_adjacent_digits(123456)); // Output: 214365
console.log(swap_adjacent_digits(12345)); // Output: false (length is odd)

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