primeNumber.html

<!DOCTYPE html>
<html>
  <head>
    <meta charset="utf-8">
    <title>Prime Number</title>
    <script type="text/javascript">
      function isPrime()
      {
        var set = 0;

        var num = document.getElementById("num").value;

        document.getElementById("answer").innerHTML = "";

        for(i=2; i<Math.sqrt(num);i++)
        {
          if(num % i == 0)
          {
            set = 1;
            break;
          }
        }

        if(set == 1)
        {
          document.getElementById("answer").innerHTML +="<h1 style='color:red'>Not a Prime  !!!</h1>";
        }
        else
        {
          document.getElementById("answer").innerHTML +="<h1 style='color:green'>Prime  !!!</h1>";
        }
      }
    </script>
  </head>
  <body>
    <div class="input-group">
      <span class="input-group-addon"></span>
      <input type="number" class="form-control" id="num" placeholder="Enter the number">
      <button onclick="isPrime()">Check</button>
      <p id="answer"></p>

    </div>
  </body>
</html>