Sep
26
2014

IsPrime Function in JavaScript

The following code sample illustrates how to use JavaScript to determine if a number provided is a prime number or not. In this example, the number is hardcoded in the JavaScript. You can edit this and experiment with other values at the isPrime at CodePen

var theNumber = 22;
var primeResult = isPrime(theNumber);
document.write("<hr />" + primeResult);

function isPrime(n) {

  var s = [2,3,5,7];
  var ld = [1,3,7,9]; 
  var divs = [];

  if (n==1) {return false;}
  if (s.indexOf(n) > -1) {return true;}
  
  if (ld.indexOf(n%10) > -1) {
     divs = getDivisibles(n);
     document.writeln(divs);
  } else {
    return false;
  }
  
  return (divs.length == 0);
  
}// isPrime

function getDivisibles(n) {
  var i = 2;
  var divs = [];
  while (i*i<=n) {
      if (n%i==0) {
        var upper = n/i;
        divs.push(i);
        if (upper>i) {divs.push(upper);}
      }
      i++;
  }// while
  divs.sort(function(x,y){return x-y;});
  return divs;
}// getDivisibles

See the Pen isPrime by J Michael Palermo IV (@palermo4) on CodePen.

    Copyright © Microsoft Corporation. All rights reserved.
    The code provided in this post is licensed under the Microsoft Public License (Ms-PL).
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