JavaScript: Find and print the first 5 happy numbers

JavaScript Conditional Statement and loops: Exercise-8 with Solution

Happy Numbers (First 5)

Happy Numbers:

According to Wikipedia a happy number is defined by the following process : "Starting with any positive integer, replace the number by the sum of the squares of its digits, and repeat the process until the number equals 1 (where it will stay), or it loops endlessly in a cycle which does not include 1. Those numbers for which this process ends in 1 are happy numbers, while those that do not end in 1 are unhappy numbers (or sad numbers)". Write a JavaScript program to find and print the first 5 happy numbers.

Visual Presentation:

Sample Solution:

JavaScript Code:

// Function to check if a number is a happy number
function happy_number(num) {
    var m, n;
    var c = [];

    // Continue loop until the number becomes 1 or enters a cycle
    while (num !== 1 && c[num] !== true) {
        c[num] = true;
        m = 0;

        // Calculate the sum of the squares of digits
        while (num > 0) {
            n = num % 10;
            m += n * n;
            num = (num - n) / 10;
        }

        num = m;
    }

    return (num === 1);
}

// Variables to track the count and current number
var cnt = 5;
var num = 1;
var f5 = '';

// Find the first 5 happy numbers
while (cnt-- > 0) {
    while (!happy_number(num))
        num++;

    f5 = f5 + (num + ", ");
    num++;
}
console.log('First 5 happy numbers are: ' + f5); 

Output:

First 5 happy numbers are : 1, 7, 10, 13, 19, 

Flowchart:

Live Demo:

See the Pen javascript-conditional-statements-and-loops-exercise-8 by w3resource (@w3resource) on CodePen.

For more Practice: Solve these Related Problems:

• Write a JavaScript function that finds the first 5 happy numbers using a helper function to compute the sum of the squares of digits.
• Write a JavaScript function that identifies happy numbers by recursively computing digit square sums until 1 is reached.
• Write a JavaScript function that prints the first 5 happy numbers by iterating through natural numbers and checking for cycles.
• Write a JavaScript function that generates an array of the first 5 happy numbers while optimizing the check for repeated cycles.

Improve this sample solution and post your code through Disqus.

Previous: Write a JavaScript program which iterates the integers from 1 to 100.
Next: Write a JavaScript program to find the armstrong numbers of 3 digits.