PALS3004: Web Programming Demo 6-3

<html>
<head>
<title>PALS3004: Web Programming Demo 6-3</title>
<script>
function button1click() {
  // get maximum value for search
  var pmax=parseInt(document.getElementById("textbox1").value);
  if (isNaN(pmax) || (pmax < 2) || (pmax > 1000000)) {
    alert("Enter value between 2 and 1000000");
    return;
  }
  // create a table of boolean values
  var table=new Array(pmax+1);
  for (var i=2;i<=pmax;i++) table[i]=true;
  // sieve of Eratosthenes
  for (var i=2;i*i<=pmax;i++) {
    if (table[i]) {
      for (var j=i*i;j<=pmax;j=j+i) table[j]=false;
    }
  }
  // report list of primes (cells remaining true)
  var primes=[];
  for (var i=2;i<=pmax;i++) if (table[i]) primes.push(i);
  var res=document.getElementById("div1");  
  res.innerHTML=primes.join(", ");
}
</script>
</head>
<body>
  <h2>Demo 6-3: Demonstrate For Loops</h2>

  <h3><a href="http://en.wikipedia.org/wiki/Sieve_of_Eratosthenes">Sieve of Eratosthenes</a></h3>
  
  <p>Generate primes up to: <input type="text" id="textbox1" size="10" >
  <button id="button1" onclick="button1click()">Go</button>
  <p><div id="div1"></div>
</body>
</html>
Demo 6-3: Demonstrate For Loops

Sieve of Eratosthenes

Generate primes up to: