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JavaScript: Find and print the first 5 happy numbers

JavaScript Conditional Statement and loops: Exercise-8 with Solution

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.

Pictorial Presentation:

JavaScript: Find and print the first 5 happy numbers

Sample Solution:-

HTML Code:

<!DOCTYPE html>
<html>
<head>
<meta charset=utf-8 />
<title>Happy Number</title>
</head>
<body>
  
</body>
</html>

JavaScript Code:

function happy_number(num) 
{
    var m, n ;
    var c = [] ;
 
    while(num != 1 && c[num] !== true) 
    {
        c[num] = true ;
        m = 0 ;
        while (num > 0) {
            n = num % 10 ;
            m += n * n ;
            num = (num  - n) / 10 ;
        }
        num = m ;
    }
    return (num == 1) ;
}
 
var cnt = 5;
var num = 1;
var f5 = ''; 
while(cnt-- > 0) 
{
    while(!happy_number(num))
        num++ ;
f5 = f5+(num + ", ") ;

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

Sample Output:

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

Flowchart:

Flowchart: JavaScript:- Find and print the first 5 happy numbers

Live Demo:

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


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Next: Write a JavaScript program to find the armstrong numbers of 3 digits.

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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