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JavaScript: Find a perfect number

JavaScript Function: Exercise-12 with Solution

Write a JavaScript function which says whether a number is perfect.

Note : According to Wikipedia : In number theory, a perfect number is a positive integer that is equal to the sum of its proper positive divisors, that is, the sum of its positive divisors excluding the number itself (also known as its aliquot sum). Equivalently, a perfect number is a number that is half the sum of all of its positive divisors (including itself).
Example : The first perfect number is 6, because 1, 2, and 3 are its proper positive divisors, and 1 + 2 + 3 = 6. Equivalently, the number 6 is equal to half the sum of all its positive divisors: ( 1 + 2 + 3 + 6 ) / 2 = 6. The next perfect number is 28 = 1 + 2 + 4 + 7 + 14. This is followed by the perfect numbers 496 and 8128.

Pictorial Presentation:

JavaScript: Find a perfect number

Sample Solution: -

HTML Code:

<!DOCTYPE html>
<html>
<head>
<meta charset=utf-8 />
<title>Find a perfect number</title>
</head>
<body>
  
</body>
</html>

JavaScript Code:

function is_perfect(number)
{
var temp = 0;
   for(var i=1;i<=number/2;i++)
     {
         if(number%i === 0)
          {
            temp += i;
          }
     }
   
     if(temp === number && temp !== 0)
        {
       console.log("It is a perfect number.");
        } 
     else
        {
       console.log("It is not a perfect number.");
        }   
 } 
is_perfect(28);

Sample Output:

It is a perfect number.

Flowchart:

Flowchart: JavaScript function: Find a perfect number

Live Demo:

See the Pen JavaScript - Find a perfect number-function-ex- 12 by w3resource (@w3resource) on CodePen.


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Previous: Write a JavaScript function which will take an array of numbers stored and find the second lowest and second greatest numbers, respectively.
Next: Write a JavaScript function to compute the factors of a positive integer.

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JavaScript: Tips of the Day

How to check whether a string contains a substring in JavaScript?

ECMAScript 6 introduced String.prototype.includes:

const string = "foo";
const substring = "oo";

console.log(string.includes(substring));

includes doesn't have Internet Explorer support, though. In ECMAScript 5 or older environments, use String.prototype.indexOf, which returns -1 when a substring cannot be found: 

var string = "foo";
var substring = "oo";

console.log(string.indexOf(substring) !== -1);

Ref: https://bit.ly/3fFFgZv